Update: I changed the docker config to "no" before booting again and the server booted all the way, got past "starting services", and started a parity check. So, it is something with docker. Still troubleshooting.
DOCKER_ENABLED="no"
Update 2: Deleted the docker image file and created a new one. Docker started without issues. I wonder if Uptime Kuma filled the docker image file up and thus made the system unstable. I will leave that docker out for now and see how stable the server is.
Update 3: The server has been stable since 3/09 now without Uptime Kuma installed.