OK, I found it. I couldn't find it earlier, because in code we have escape characters before '. The code is in file vbenterprisetranslator_functions_hooks.php
Code:
$vbulletin->templatecache['forumhome_lastpostby'] =
'$lastpostinfo[\'lastposter\'] = \'<!--vBET_SNTA-->\' . $lastpostinfo[\'lastposter\'] .\'<!--vBET_ENTA-->\';'
.$vbulletin->templatecache['forumhome_lastpostby'];
I cannot reproduce the issue so I'm not able to check solution. Please describe how to reproduce or try to replace the code with the one below. This solution was not checked.
Code:
$vbulletin->templatecache['forumhome_lastpostby'] =
'$lastpostinfo[lastposter] = \'<!--vBET_SNTA-->\' . $lastpostinfo[lastposter] .\'<!--vBET_ENTA-->\';'
.$vbulletin->templatecache['forumhome_lastpostby'];
This can be it - error code tells about unexpected ' and since vBulletin puts our code in " (eval('$final_rendered = "' . $template_code . '";');) this could lead to the error. Please tell us, how to reproduce, or check possible solution and send us your status.