I have also had this happen several times. Once you get this error message the LBK is basically useless. Check though that all the views/pmk's are present, I had one floorplan that spooked as a used drawing but was invisible so removed it and that solved the problem.
A workaround that worked for me is to open a new layoutbook and import all your layouts from the damaged LBK into the new one. Save this LBK with a different name and presto. If you still get an error message then you should repeat the above procedure except import one layout at a time and save after each import. This way you narrow down the offending layout.
I recommend you tick the icon to make a backup in your PM preferences.
Regards
Nick
ArchiCAD 4.1–22, Mac OS 10.14.x iMac 27" 3,2Ghz Intel-Core i5