Weird artifacts showing up inside multitrack session

Hey, has anyone experienced this?...

I recently recorded an audiobook and as I was going through the final pass of edits, I kept finding random tracks with weird artifacts from totally different multitrack recording sessions, for totally different projects, spliced inside the tracks. 

I had to go back and re-record multiple tracks, only to find that new artifact splices would pop up somewhere else.  It feels a bit like playing whack-mole...

Any advice? Bug fixes? Thoughts on what this could be?

Thanks!