In view of the fact that most users of ArchiCAD are PC users, and that you are more-or-less alone in this problem, have you considered that it might be your machine?
A strategy for dealing with uncooperating files is to merge them into new projects - just as a test.
This is likely a hard drive issue.
What is your hardware setup?
BTW - on this forum it is common for members to list their hardware and software configurations to narrow the possibilities.
Dwight Atkinson