ERROR: var_export(): Cannot use output buffering in output buffering display han

Dear sirs,
I am reporting, that after today’s plugin update to 3.1.2. I have got this error message on the updated WP website http://www.skidestne.cz:
ERROR: var_export(): Cannot use output buffering in output buffering display handlers
Until update previous version worked properly. The database is backuped but the progress stops at 25% at WP XML Export and restarts after 5 mins without success.

My job is set do not backup files (only db, Wp XML and plugins list), so max. latest successfuly backuped files are about 287 kB large.
Plain WP content XML Export (All – Posts, Pages, …) from WP menu works in seconds and ok.

PS: I can forward my error log to an email, if it wont be well formated and readable below. Just ask for it.

Could you help me with this strange issue?
Thank you
Alois

Log:

[INFO] BackWPup version 3.1.2; A project of Inpsyde GmbH<br />
[INFO] WordPress version 3.8.1<br />
[INFO] Blog url: http://www.skidestne.cz/<br />
[INFO] BackWPup job: Záloha databáze a XML Export WP; DBDUMP+WPEXP+WPPLUGIN<br />
[INFO] BackWPup cron: 0 3 * * *; Next: St, 5 Bře 2014 @ 03:00<br />
[INFO] BackWPup job started manually<br />
[INFO] PHP ver.: 5.2.6-1+lenny8; apache2handler; Linux<br />
[INFO] Maximum PHP script execution time is 30 seconds<br />
[INFO] MySQL ver.: 5.0.51a-24+lenny3<br />
[INFO] Temp folder is: /var/www/skidestne/wp-content/uploads/backwpup-3cc42c-temp/<br />
[INFO] Logfile is: /var/www/skidestne/wp-content/uploads/backwpup-a6fdb-logs/backwpup_log_3cc42c_2014-03-04_21-22-54.html<br />
[INFO] Backup type is: archive<br />
[INFO] Backup file is: /var/www/skidestne/zaloha-db-wordpress/backwpup_7140e9_2014-03-04_21-22-54.zip<br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 155|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 19]">[04-Bře-2014 21:22:54]</span> <samp>1. Try to backup database …</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 169|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 21]">[04-Bře-2014 21:22:54]</span> <samp>Connected to database skidestne on localhost</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 23]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_commentmeta" with "0" records</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 24]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_comments" with "0" records</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 25]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_links" with "0" records</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 26]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_microblogposter_accounts" with "0" records</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 27]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_microblogposter_logs" with "0" records</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 28]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_nxs_log" with "0" records</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 23,75 MB|Mem Max: 23,75 MB|Mem Limit: 256M|PID: 12975|Query's: 29]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_options" with "1222" records</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 31]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_postmeta" with "1179" records</samp><br />
<span datetime="2014-03-04T21:22:54+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 34]">[04-Bře-2014 21:22:54]</span> <samp>Backup database table "wp_posts" with "388" records</samp><br />
<span datetime="2014-03-04T21:22:55+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 36]">[04-Bře-2014 21:22:55]</span> <samp>Backup database table "wp_term_relationships" with "200" records</samp><br />
<span datetime="2014-03-04T21:22:55+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 38]">[04-Bře-2014 21:22:55]</span> <samp>Backup database table "wp_term_taxonomy" with "6" records</samp><br />
<span datetime="2014-03-04T21:22:55+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 40]">[04-Bře-2014 21:22:55]</span> <samp>Backup database table "wp_terms" with "6" records</samp><br />
<span datetime="2014-03-04T21:22:55+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 42]">[04-Bře-2014 21:22:55]</span> <samp>Backup database table "wp_usermeta" with "77" records</samp><br />
<span datetime="2014-03-04T21:22:55+00:00" title="[Type: 1024|Line: 204|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 44]">[04-Bře-2014 21:22:55]</span> <samp>Backup database table "wp_users" with "3" records</samp><br />
<span datetime="2014-03-04T21:22:55+00:00" title="[Type: 1024|Line: 251|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 47]">[04-Bře-2014 21:22:55]</span> <samp>Added database dump "skidestne.sql" with 1,12 MB to backup file list</samp><br />
<span datetime="2014-03-04T21:22:55+00:00" title="[Type: 1024|Line: 257|File: wp-content/plugins/backwpup/inc/class-jobtype-dbdump.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 47]">[04-Bře-2014 21:22:55]</span> <samp>Database backup done!</samp><br />
<span datetime="2014-03-04T21:22:55+00:00" title="[Type: 1024|Line: 114|File: wp-content/plugins/backwpup/inc/class-jobtype-wpexp.php|Mem: 24,00 MB|Mem Max: 24,75 MB|Mem Limit: 256M|PID: 12975|Query's: 48]">[04-Bře-2014 21:22:55]</span> <samp>1. Trying to create a WordPress export to XML file …</samp><br />
[04-Mar-2014 21:22:57] PHP Fatal error:  var_export(): Cannot use output buffering in output buffering display handlers in /var/www/skidestne/wp-content/plugins/backwpup/inc/class-job.php on line 1155<br />
<span datetime="2014-03-04T21:22:57+00:00" title="[Type: 1|Line: 1155|File: wp-content/plugins/backwpup/inc/class-job.php|Mem: 28,50 MB|Mem Max: 31,25 MB|Mem Limit: 256M|PID: 12975|Query's: 1142]">[04-Bře-2014 21:22:57]</span> <samp style="background-color:red;color:#fff">ERROR: var_export(): Cannot use output buffering in output buffering display handlers</samp><br />
[04-Mar-2014 21:22:57] PHP Fatal error:  var_export(): Cannot use output buffering in output buffering display handlers in /var/www/skidestne/wp-content/plugins/backwpup/inc/class-job.php on line 1155<br />
<span datetime="2014-03-04T21:27:59+00:00" title="[Type: 512|Line: 610|File: wp-content/plugins/backwpup/inc/class-job.php|Mem: 22,75 MB|Mem Max: 22,75 MB|Mem Limit: 128M|PID: 12964|Query's: 8]">[04-Bře-2014 21:27:59]</span> <samp style="background-color:#ffc000;color:#fff">WARNING: Job restarts due to inactivity for more than 5 minutes.</samp><br />
<span datetime="2014-03-04T21:27:59+00:00" title="[Type: 1024|Line: 114|File: wp-content/plugins/backwpup/inc/class-jobtype-wpexp.php|Mem: 23,25 MB|Mem Max: 23,25 MB|Mem Limit: 256M|PID: 12964|Query's: 11]">[04-Bře-2014 21:27:59]</span> <samp>2. Trying to create a WordPress export to XML file …</samp><br />
[04-Mar-2014 21:28:02] PHP Fatal error:  var_export(): Cannot use output buffering in output buffering display handlers in /var/www/skidestne/wp-content/plugins/backwpup/inc/class-job.php on line 1155<br />
<span datetime="2014-03-04T21:28:02+00:00" title="[Type: 1|Line: 1155|File: wp-content/plugins/backwpup/inc/class-job.php|Mem: 28,00 MB|Mem Max: 30,75 MB|Mem Limit: 256M|PID: 12964|Query's: 1110]">[04-Bře-2014 21:28:02]</span> <samp style="background-color:red;color:#fff">ERROR: var_export(): Cannot use output buffering in output buffering display handlers</samp><br />
[04-Mar-2014 21:28:02] PHP Fatal error:  var_export(): Cannot use output buffering in output buffering display handlers in /var/www/skidestne/wp-content/plugins/backwpup/inc/class-job.php on line 1155<br />
<span datetime="2014-03-04T21:29:19+00:00" title="[Type: 256|Line: 1173|File: wp-content/plugins/backwpup/inc/class-job.php|Mem: 30,00 MB|Mem Max: 30,00 MB|Mem Limit: 256M|PID: 13073|Query's: 11]">[04-Bře-2014 21:29:19]</span> <samp style="background-color:red;color:#fff">ERROR: Aborted by user!</samp><br />
<span datetime="2014-03-04T21:29:19+00:00" title="[Type: 1024|Line: 1198|File: wp-content/plugins/backwpup/inc/class-job.php|Mem: 30,00 MB|Mem Max: 30,00 MB|Mem Limit: 256M|PID: 13073|Query's: 12]">[04-Bře-2014 21:29:19]</span> <samp>One old log deleted</samp><br />
<span datetime="2014-03-04T21:29:19+00:00" title="[Type: 256|Line: 1204|File: wp-content/plugins/backwpup/inc/class-job.php|Mem: 30,00 MB|Mem Max: 30,00 MB|Mem Limit: 256M|PID: 13073|Query's: 13]">[04-Bře-2014 21:29:19]</span> <samp style="background-color:red;color:#fff">ERROR: Job has ended with errors in 385 seconds. You must resolve the errors for correct execution.</samp><br />

Info from Settings:

Setting	Value<br />
Setting	Value<br />
WordPress version	3.8.1<br />
BackWPup version	3.1.2 Get pro.<br />
PHP version	5.2.6-1+lenny8<br />
MySQL version	5.0.51a-24+lenny3<br />
cURL version	unavailable<br />
WP-Cron url:	http://www.skidestne.cz/wp-cron.php<br />
Server self connect:	Response Test O.K.<br />
Temp folder:	/var/www/skidestne/wp-content/uploads/backwpup-3cc42c-temp/<br />
Log folder:	/var/www/skidestne/wp-content/uploads/backwpup-3cc42c-logs/<br />
Server	Apache/2.2.9 (Debian) PHP/5.2.6-1+lenny8 with Suhosin-Patch mod_python/3.3.1 Python/2.5.2 mod_perl/2.0.4 Perl/v5.10.0<br />
Operating System	Linux<br />
PHP SAPI	apache2handler<br />
Current PHP user	skidestne<br />
Safe Mode	Off<br />
Maximum execution time	30 seconds<br />
Alternative WP Cron	Off<br />
Disabled WP Cron	Off<br />
CHMOD Dir	0755<br />
Server Time	21:8<br />
Blog Time	22:08<br />
Blog Timezone	Europe/Prague<br />
Blog Time offset	1 hours<br />
Blog language	cs-CZ<br />
MySQL Client encoding	utf8<br />
Blog charset	UTF-8<br />
PHP Memory limit	256M<br />
WP memory limit	40M<br />
WP maximum memory limit	256M<br />
Memory in use	30,25 MB<br />
Loaded PHP Extensions:	PDO, Reflection, SPL, SimpleXML, apache2handler, bcmath, bz2, calendar, ctype, date, dba, dom, exif, filter, ftp, gd, gettext, hash, iconv, json, libxml, mbstring, mcrypt, mime_magic, mysql, mysqli, openssl, pcre, pdo_mysql, posix, session, shmop, soap, sockets, standard, sysvmsg, sysvsem, sysvshm, tokenizer, wddx, xml, xmlreader, xmlwriter, zip, zlib<br />

https://wordpress.org/plugins/backwpup/