Can not remove Master Page overrides
After 25 years of FM experience I'm "at the end of my Latin" in FM-15.0.8.979
For the attached FM file this is the situation when switching from Master Page display to Body Page display:

Of course I want to remove these overrides:
- Set Remove Overrides and use Continue → Switching to MP view and back to BP view issues the vey same message.
- MIF wash the document → the overrides are still there and can not be removed by the mentioned method.
- Re-assign the master pages (1 → First; 2…65 → Right/Left) → Overrides still there.
- Create new document, import all formats, then copy the contens of the flow → Overrides are back...
- Assign R/L MPs to all pages (no special page 1) → Overrides still there.
- Opening the document in FM-16.0.4.1062 → same debacle.
A visual inspection of the pages do not show me any deviations from the layout defined by the MPs - so what is the nature of these overrides?
