There appears to be an issue with a this and a couple mods. In this case structures from mo structures are generating with the locks being immediately popped off of some chests which generate and get converted to lootr.

Forge: 1.16.5 36.2.28
Lootr: 1.16.5-0.1.11.38.jar
Locks: 1.16.5-3.0.3.jar
Mo structures: forge-1.2.0-1.16.5.jar

and seemingly villages and better dungeons seems to be just fine. and so do dungeons arise from a glance at a couple locations.

o-oh.... well... thats a top frick. D: and I guess it's not something you can/be willing to work on cause locks is old and kinda semi-abandoned?
although it's strange that the bug only happened with this specific structures I mentioned and not others?

I'm afraid Locks and Lootr aren't compatible as of recent updates.

I'm assuming it's some sort of race condition. And apologies, I'm not able to take on the Locks mod at this time.