Browsing content on Apple TV causes Plex server to lock up

Network share is extremely unreliable unless you do it perfectly.

I show how to do that here

Really NOT advised.

How about an iSCSI target ? That’ll be secure enough and won’t lock on you.

The fundamental issue here is file locking on the block device – none of which is guaranteed over any network sharing protocol except when the target is an iSCSI device.