Could be anything.

Something decides it’s going to fill your disk up with noise and plex enters a crash loop as it can’t write to disk any more.

Your reverse proxy decides it’s not going to issue valid SSL certificates so all your plex clients refuse to connect.

One day an OS update decides your network configuration wasn’t important, and your OS throws a shit fit because there’s no route to 192.168.1.100 any more

Not OP. But i do the same.

I have multiple proxmox hosts, running multiple VMs, each running containers.

I do it so I can minimise disruption. Fixing a fault in immich doesn’t mean the house is without plex for a week.

You can self heal after a vasectomy. It’s rare but happens. Especially in the first few years following the procedure.

But easy enough to go to your dr every few years and get tested.