I’m having the same issue. Here’s a simple repro, but it happens all the time. Basically, it seems like there are certain barriers for undo that I can’t control like “can’t undo after applying lighting” or “can’t undo after world load”. There are simply steps that the history isn’t tracking, it seems. Here’s my simple repro:
- Select any geometry in your level (I selected a wall)
- right-click in the world outliner and select “pilot” so it follows you around in the viewport (this is an odd thing to do, I know, but it’s an example of one of the many operations that don’t seem to be undoable).
- exit from pilot after you’ve moved around.
- Observe that you cannot undo to put the wall back where it was before piloting it. You have to manually move it back.
I’m on version 4.18.
Obviously, this is a very concerning issue. It’s unnerving since I experiment a lot and end up getting myself into bad states where I have to hook things back up after an undo barrier.