It’s decided!
These were not duplicates of the actor.
[But it was a bug]
This actor was placed on all (Sublevels), but on each map, in different positions.
For some unknown reason, when I clicked the (Compile) button, all these objects became visible, despite the fact that they themselves (Sublevels) were hidden.
Copying the map or deleting the object and pasting it back did not help.
The solution was to open each (Sublevel) in turn, and click (Compile) for (Actor), which was “broken”.
