Randomly unable to login

[Telefonkatalogen]

Hi guys. 

I was hoping I'd never have to post my own issues here as this forum has always been able to solve them, but I'm out of luck right now and hoping someone can help.   

My UPS crashed a few days ago, causing the server to abruptly shut down. After booting up again, all seemed fine, until Jellyfin just stopped working last night. When checking in Proxmox, I saw a that the disk usage and CPU usage in the summary tab were super high, and restarting the LXC did not help. Therefore, I just restored a backup from a week ago and thought I was super smart.  
Sadly, it only lasted for about 12 hours, as right now no devices are allowed to log on with username and password. The only way to log on with any device is to use the QuickConnect function. Luckily I still had a browser that was not logged out.   
Once logged in, everything works just fine, but I still need to get it fixed.   

Does anyone have any idea where to start?   

I tried uploading the .log file and a text file, but both were incompatible file types. If you know what file type it should be, I'll convert and upload ASAP. 

Thank you so much in advance!

[Telefonkatalogen]

OK, so I kept pounding at this issue on my own as I could not find anything relevant in the logs at all, and finally managed to crack the code...

My LXC did not have NTP installed and was set to the wrong timezone, not accounting for it now being CET and not CEST.
A simple "date" in console revealed it, and it was an easy fix with sudo timedatectl set-timezone Europe/"Your location".
Restarted Jellyfin and everything works as it should again.

I'm leaving this post up so others can see it if they have similar issues in the future.
Thanks to all who read and spent time trying to help!

Edit: This only solved it temporarily. var/cache was completely full, over 15 GB. Limit on the installation is 20 GB, so the LXC was out of space. Deleted it all and it's working again.
Not sure what causes it to bloat, but I'll keep searching for the culprit. I'm guessing old transcodes, so first step is enabling the "Delete segments" under Playback -> Transcoding.