Please do not PM regarding support ...
Code: Select all
[08/Jan/2018:20:00:58 +0100] "GET /app.php/livetopicupdate/78/6?sid=79dedf634a287a9d298a255b9eb7aa92 HTTP/1.1" 500 221 "https://forums.volgeop.eu/viewtopic.php?f=90&t=78" "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/
This suggests that the Live Topic Update extension might be the cause of your troubles.
So Disable that extension, note disable, not just delete the folder or delete it from the database.
Disabling it through the Customize tab in your ACP.