Fatal error: DateTimeZone::__wakeup(): Timezone initialization failed

Hello,

We noticed the following error in WordPress 4.6:

Fatal error: DateTimeZone::__wakeup(): Timezone initialization failed in /home/user/public_html/site.com/wp-content/object-cache.php on line 240

which checking the strace appeared to be related to the bwp-recaptcha:

7792 4375  sendto(4, "get f9063c7ce78342ec9504bb649symeu_:bwp_plugins:timezone\r
", 58, MSG_NOSIGNAL, NULL, 0) = 58
7793 4375  recvfrom(4, 0x1e9ab48, 8196, 16384, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
7794 4375  poll([{fd=4, events=POLLIN}], 1, 5000) = 1 ([{fd=4, revents=POLLIN}])
7795 4375  recvfrom(4, "VALUE f9063c7ce78342ec9504bb649symeu_:bwp_plugins:timezone 4 24\r
O:12:\"DateTimeZone\":0:{}\r
END\r
", 8196, MSG_NOSIGNAL, NULL, NULL) = 96
7796 4375  open("php_errorlog", O_WRONLY|O_CREAT|O_APPEND, 0644) = 6
7797 4375  write(6, "[18-Aug-2016 10:31:23 UTC] PHP Fatal error:  DateTimeZone::__wakeup(): Timezone initialization failed in /home/user/public_html/site.com/wp-con     tent/object-cache.php on line 240
", 192) = 192

Website runs with PHP Version 5.6.24 and as far as we could see the issue is caused by the way how timezone is called in wp-content/plugins/bwp-recaptcha/vendor/kminh/bwp-framework/src/class-bwp-framework-v3.php file.

Could you please check?

Thank you!

https://wordpress.org/plugins/bwp-recaptcha/