If something is blocking the One File Per Actor file, you can delete the actor inside Unreal, but the file won't be deleted and will reappear after the map is reloaded.

Licensee:
Artist reported removed actors reappearing

I suspect that file got loaded by something and tested what going to happen if you open a file for read

I used python to test

lock_file = R'Content\__ExternalActors__\empty\2\EZ\0RUFESHPBMMD8KGHEWO1O0.uasset'
f = open(lock_file, 'r')

you can delete the actor inside Unreal

it would look like everything fine

but the file won't be deleted and will reappear after the map is reloaded (but in 5.0 you need to reload engine)

It will try to ask for save of unload but I think actor should not be removed in that case or error/warning should be more obvious

There also an error that is a warning

LogFileManager: Warning: Error deleting file: D:/other/unloaded_actors/Content/ExternalActors/empty/2/Q2/JZ2L80I7AEC44B7IED0BYR.uasset (Error Code 32)

in 5.0 it also wasn't updating after map reload

Thank you