I have the exact same problem. The file seems to corrupt itself upon reopening. I have a backup from about a week ago that I can restore, but like you, it re-corrupts when I close and reopen it. So frustrating. Have you gotten anywhere?
FYI I have another install on a laptop that's not doing this, so I don't think it's inherently something in the file that's corrupt. The data also has no issues when I verify/rebuild.
