Oh, my. I was having such a stupid problem.
When going to "File" selecting one of the bottom-most drawings the oddest thing would happen! A completely different drawing from the one selected, a different name and from a different job directory entirely, would open! (Yes, I know - pretty old school to do that instead of the big red "A", but...creature of habit)
This happened repeatedly, until I had a moment to ponder.
Then, it occurred to me! I wondered if, by chance, I had those drawings "Pinned" in the list at the big read "A". (I've only just used that handy little "Pin" feature a handful of times, and quite some time ago, at that.
BUT, sure enough, the drawings that were opening were pinned drawings. And this occurred even though those drawing names were NOT listed in my 9 under "File."
All I had to do was unpin those pesky offenders.
Phew. What a relief to know that my AutoCAD wasn't somehow corrupt or that I wasn't losing my mind!