XF 2.1 Replier can only add posts at the end of a thread

[siONtI]

I started getting this error on admin panel since 2.1.3 update
This error happens only on 1 thread (most popular/active thread on my forum)

LogicException: Replier can only add posts at the end of a thread src/XF/Service/Thread/Replier.php:182
Generated by: Username Oct 14, 2019 at 7:02 PM

Stack trace
#0 src/XF/Service/Thread/Replier.php(165): XF\Service\Thread\Replier->setPostPosition(Array)
#1 src/XF/Service/ValidateAndSavableTrait.php(40): XF\Service\Thread\Replier->_save()
#2 src/XF/Pub/Controller/Thread.php(461): XF\Service\Thread\Replier->save()
#3 src/XF/Mvc/Dispatcher.php(321): XF\Pub\Controller\Thread->actionAddReply(Object(XF\Mvc\ParameterBag))
#4 src/XF/Mvc/Dispatcher.php(244): XF\Mvc\Dispatcher->dispatchClass('XF:Thread', 'AddReply', Object(XF\Mvc\RouteMatch), Object(SV\ElasticSearchEssentials\XF\Pub\Controller\Thread), NULL)
#5 src/XF/Mvc/Dispatcher.php(100): XF\Mvc\Dispatcher->dispatchFromMatch(Object(XF\Mvc\RouteMatch), Object(SV\ElasticSearchEssentials\XF\Pub\Controller\Thread), NULL)
#6 src/XF/Mvc/Dispatcher.php(50): XF\Mvc\Dispatcher->dispatchLoop(Object(XF\Mvc\RouteMatch))
#7 src/XF/App.php(2178): XF\Mvc\Dispatcher->run()
#8 src/XF.php(390): XF\App->run()
#9 index.php(33): XF::runApp('XF\\Pub\\App')
#10 {main}


Request state
array(4) {
["url"] => string(47) "/threads/threadnamehere.8012/add-reply"
["referrer"] => bool(false)
["_GET"] => array(1) {
["/threads/threadnamehere_8012/add-reply"] => string(0) ""
}
["_POST"] => array(9) {
["message_html"] => string(82) "<p>message here</p>"
["attachment_hash"] => string(32) "360a5a64cf4caad9a23ddd1bc75cb559"
["attachment_hash_combined"] => string(86) "{"type":"post","context":{"thread_id":8012},"hash":"360a5a64cf4caad9a23ddd1bc75cb559"}"
["last_date"] => string(10) "1571019068"
["last_known_date"] => string(10) "1571071636"
["_xfToken"] => string(8) "********"
["_xfRequestUri"] => string(47) "/threads/threadnamehere.8012/page-1567"
["_xfWithData"] => string(1) "1"
["_xfResponseType"] => string(4) "json"
}
}

 

[AndyB]

The last post of that thread, what is the date?