except that wayward fstab thing has reappeared, where fstab has mistakes in it that weren't there before
Isn't this a great chance to find out if a package in the test repo is causing it?
At least one other user (Magnus Johansson) seems to have used the test repo when bitten by fstab. And the question was never asked (if the test repo was enabled) in the other cases.
I usually don't suggest how someone else shall spend his days, but if DBeckett has a day off this is a great opportunity.
Is fstab modified if the upgrade is repeated on a clean install? And is it possible to upgrade a few packages at a time to find the culprit, if there is one?