Are you using subtitle sync in bazarr? I don’t use jellyfin, but have found that bazarr has fixed most of my subtitles that were not in sync just by enabling the option. I think it’s CPU intensive though, so don’t do the whole library at once.

Did you change the native VLAN to IoT or just added the tag and left the native VLAN on the switch port set to default? You should be able to change the native VLAN and leave tagged VLANs as “allow all”.

My only other thought is how did you isolate the IoT network and are you able to access other devices from default to IoT?

I’ve had it running for a few months, I don’t use it that often but it’s been super handy when I need it.