Update 5 (May 11): Alright, so it crashed again a while ago, so I switched from SWAG to NGINX, and ever since then it's been flawless (uptime is currently at 15+ days). If anyone else sees this, maybe give this a shot if you're in a similar situation. I'm not sure why or what caused this, but hey, I'll take it.
Update 4: So far since I deleted my custom Docker network and undid all custom network changes, it seems to be more stable. I had to go in and manually delete some configuration files, but so far so good. If it keeps working, I'll probably switch from SWAG to NGINX and see if that helps prevent it going forward since I don't trust SWAG anymore.
Update 3: Still crashing at around that same time, and the other system I had open decided to reboot and close the log windows (thanks Windows Update). I did notice that SWAG tries to renew its security certificates at around the time every day where the last syslog is made, exactly an hour before it's crashed multiple times. Disabling it and deleting every trace of a VPN tunnel, put everything that was routed through it back to bridge mode, and give that a shot.
Update 2: I decided to go back to 6.11.5 and have another system open and was going to leave that running constantly, but with logs open for all Docker containers so I would be able to monitor those, and I noticed that suddenly a lot of containers were giving an error. Rebuilding the Docker image now and going to see if maybe that's what was going funky.
Update: 6.9.2 continued to seem to be just fine, I gave 6.12-rc3 a shot, and it ended up doing the same thing. I did notice that it was also within a few minutes of the time at which it's crashed before, so I'm thinking whatever is running at around 3am is causing it...now to find out what it is.
Syslog also continued to be of no use, so it's gotta be a Docker or plugin causing it (if that makes sense).