I think that whats happening is due to the end stop of the door, especially if you have family members that bang the door open or closed against whatever stops it. The shock is transmitted into that fastener, which eventually starts it moving.
If it were mine, I’d research Loctite options for dealing with thread locking in a high vibration environment.
If it has to come apart again, I’d also consider mortising in some rollers on the bottom.
And does anyone make something akin to a “soft close” mechanism for pocket doors? Something to keep it from banging hard against the stops.