Sublevel Duplicates

G’day. Spent a few hours moving actors into existing streaming sublevels to try and free up some memory and ended up with a sickening mess of duplicates. Had a couple of crashes and reverted back to the original maps. Is this a known issue ? Any hints on best practice ?

Righto after having another go at it the problem occurs if you only save the sublevels while editing and there is an unexpected shutdown of the editor this creates duplicates as the Persistent level wasn’t saved. Go slow, save all often.