What EXACTLY happens when you try do do the CTRL+ALT+C
Compacting family file.... The information in the specified file has been damaged and cannot be used. Please revert to a backup (*.FBK) file.
What happens when you do the Privatize file command?
Privatizing your file temporarily ... Do you still want to temporarily privatize this file? Privatizing family file... The information in the specified file has been damaged and cannot be used. Please revert to a backup (*.FBK) file.
When you do a CAS+UpArrow are there still errors? No errors
CAS+RightArrow This file was improperly closed and opened 31 time(s). The current internal version number is #38. Its previous internal version number was #38.
Index Check: completed Cache Check: completed
I found the article on repairing a damaged data file. Steps 1 (compressing, see above), 2 (rebuilding indexes, no errors), 3 (File Fixer, no errors), 4 (exporting individuals, fails during save, same message as above). Option 5 (gedcom export / import) worked but with some questionnable facts (nr of family names decreases, nr of text records increases).