Off topic. Can I suggest you to also explore Jellyfin instead of Plex? Just give it a shot before you pay to Plex folks is all I am asking. Use whichever you find better.
I had a lot of freezing when I was using immich on my RPi4. May be due to ram constraints. I moved to a 7 8 year old PC that I had lying around. It’s less finicky than a Pi4.
I ended up using spacers so that it does not come in contact with the metal box enclosure. Thanks for pointing out the mountijg holes. It was right there and I never noticed haha. I feel like an idiot.