Below shows that when I copy/mirror and then delete the mirrored copies, the originals are deleted as well. (Not shown: If I insert a door into the mirrored copies, the original develops a hole where the door was added to the copy.) As you can see, there are solids added to the walls. Not sure it that’s a factor. Rhino 6 (Current), Current Va version.
I still cannot reproduce the issue using the last uploaded model.
How are you copying the objects?
Which command are you using?
I thought you were using the Mirror command, but in the GIF I can’t see what are you typing/clicking, and it seems you’re not specifying a mirror plane/line using the mouse.
Does it happen with any wall in this document or only with some walls in particular?
Update: I’m not able to reproduce this behaviour after installing some driver updates. This may have been the problem. On the other hand, some of these issues occur intermittently, and this may be one of those. I’ll be on the lookout.
Edit: It’s definitely still an issue. Though deleting a copied wall doesn’t seem to often delete the original wall (as the original post showed) placing a door or window, after the mirror, in either copy or original wall usually causes a doppleganger opening in the other. Moving a door or window back and forth seems to’remind’ the wall that the rogue opening doesn’t belong, but there’s definitely an undesired resonance between original and copied walls when windows and doors are placed in them.