Hi
I think I can reproduce this behavior although it does not happen consistently.
I have a WL 12 Project template with tabs and layout. This works perfectly.
In a Tab within the Project I create a montage from an existing wav file. Save that as ‘other’ to a specific folder destination.
Double click the new montage to make it ‘full size’ and add a marker or anything… Double click the Montage again to return it to ‘normal size’. The Layout has changed (specifically Tool Windows which were there have disappeared).
Click on another Montage in the same Tab group … the correct Layout sometimes re appears. Going to another Tab seems to result in the Layout re appearing correctly.
I’m on Windows 10 current build.
Image 01 Correct Layout
Image 02 Full Sized Montage
Image 03 Incorrect Layout
Image 04 Correct Layourt restored.