Has this occurred in just this one file or can you reproduce this in other files?
A crash that only occurs in a particular file may mean that the file is damaged. (And the crashes themselves can damage your file--so cause and effect can be difficult to determine here.)
It's possible the file became corrupted. It's only a month old. Each time it crashed I reverted to a good backup.
I deleted the layout separators and created new ones. I can now scroll back and forth past the separators without crashing the file.
One of the separators must have become corrupted as layouts or layout elements sometimes do. it wasn't through crashing, though.
Seems like a pretty new file to be corrupted.