InDesign Corrupt File Error

For three days I’ve been getting new errors (attached) on two multi-page almost-completed files I’ve been working on for weeks. I’m running the latest update from Creative Cloud. Even uninstalled and reinstalled an older version to see if it was a bug in the latest update. Worked for a couple of hours but first thing this morning I got errors on both files again. Created brand new InDesign files and copy/pasted text and graphics from the old to see if that would help. Didn’t.