I tried several scenarios with mixed results.
Opened the program fresh and creating two new files. Everything was fine.
Opened several old files with the two new files open. Everything seemed fine.
Closed the new files and opened old files. Was fine at first, but after three things started going wonky (missing tabs/buttons, grey bars instead of rulers).
Started fresh and opened old files. Everything was wonky.
I will send two of the files and related assets for review.
Thank you!