Sorry for the delayed response.
I just set up a php.log this morning and attempted to export to CSV using the plug-in, but it did not record any errors to the php.log file.
However, it does generate this error each time on the HTML error.log file:
[Fri Sep 04 07:50:54 2015] [error] [client 73.19.195.225] Premature end of script headers: admin-ajax.php, referer: http://www.knoxmercury.com/wp-admin/admin.php?page=wp-ultimate-csv-importer%2Findex.php&__module=export
