Okay so I took a little look while we wait on Tom 
There is loads of this stuff, over 2000 of them in the hour up to the crash …
Feb 19, 2022 01:40:12.670 [14472] ERROR - [TranscodeOutputStream] Unable to allocate RingBuffer for transcode
… and the only topic I can see on this forum that has any reference to this error is from Plex Media Server has stopped working - #5 by sa2000 which is a very old topic which talks about memory allocation.
Also in your logs I see this …
Feb 19, 2022 01:39:29.870 [15608] DEBUG - Photo cache obtained 1024530 bytes from http://127.0.0.1:32400/library/metadata/128702/thumb/1645237358
Feb 19, 2022 01:39:29.870 [15608] DEBUG - Saving original media file to E:\Plex Media Server\Cache\PhotoTranscoder\2f\2f866e4fd00fea706e842e1abeb5fd9410fffe49.jpg
Feb 19, 2022 01:39:29.872 [15608] ERROR - Format [JPEG] - Insufficient memory (case 4)
Feb 19, 2022 01:39:29.872 [15608] ERROR - Error resizing an image, we don't trust what we cached [E:\Plex Media Server\Cache\PhotoTranscoder\2f\2f866e4fd00fea706e842e1abeb5fd9410fffe49.jpg]
… which again seems to indicate some memory problem. What time do you have the plex Scheduled Tasks to run at ? If its 2am then my guess is that up until that point your system is under stress but staying alive and then when maintenance kicks in it blows the server up and crashes.
I also see a dmp was created at Feb 19, 2022 02:00:03.093 [6228] ERROR - Trashing E:\Plex Media Server\Crash Reports\1.25.6.5545-c8bd13540\PLEX MEDIA SERVER\4b581f67-ec2f-4a20-b02a-cbb6fe528a55.dmp so maybe Tom or someone from plex could take a look at that.
One thing I’m somewhat interested in is the PhotoTranscoder and those errors. What size is your E:\Plex Media Server\Cache\PhotoTranscode folder ? This cache can grow unbounded to crazy levels (see Cache/PhotoTranscoder Folder Size Sanity Check for some context). What might be worth a try if nothing else is to nuke this cache completely (delete everything under PhotoTranscode) and see if the server crashes again tonight. Make sure plex is not running when you delete it. Plex starts creating a new cache so its very safe to delete it (I delete mine weekly).
Over to @tom80H for additional comments and recommendations.
