It frequently happens that I'll have eight or nine drawings open to make changes.  After I've made the changes, I'll click "Save All", which SolidWorks executes properly.  I then proceed to close the drawings one by one.  After closing about three drawings, SolidWorks starts asking if I want to save the drawings before closing them.  After this point, Save All doesn't work any more, and I have to save each drawing one at a time when I close them.  The questions are A) why does Save All quit working, and B) why does SolidWorks decide that drawings I just saved need to be saved again?

To be clear, this doesn't happen with just drawings.  It can happen with any grouping of files.