To delete a playback loop override within an existing playback loop, first select the take that contains the loop and show only that take’s player in the graphic editing view. Playback loop markers will appear in the time line. Click on the override marker in the measure that you wish to revert and press the delete key to delete the override. When the override is removed, the take will revert to playing and showing ghosts of the original looping notes (with square edges). It is important to note that deleting an override does not delete whatever extra notes were recorded within the override. If you override the measure again, those notes will appear again. If you want the notes in your override to be deleted as well, select them and delete them before you delete the override marker.
When you add a playback loop to a take which contains existing notes beyond the end of the loop source, the playback loop will act like an opaque layer on top of whatever notes were previously recorded. Repeating notes will temporarily obscure whatever used to be in the repeat bars until the playback loop is removed -- at which time the old notes will become visible again. When you override a playback loop in a given measure, it is like cutting a hole in the opaque layer and looking through to the raw take underneath. Hence, if you add a playback loop to a take which obscures a group of old notes, you may be surprised to find them popping up in your override measures. To avoid this, delete unwanted notes from a take before adding a playback loop.