Hello && welcome @Corsade
This issue could be many things, we need to narrow it down, If you can post your Graylog-Sidecar configurations ( just one would be fine) , Input used /w configurations. Any log files not only on Graylog-Server but any logs from the GL sidecar. Reminder, when posting please use the markdown for logs and configurations so its easier to read, You can find out here
thanks