Apparently the reacquisition of files happens by itself. I've run the validation several times, and a couple times I noticed a small download happening. I finally got it to show 0 files that failed to validate, but I still get the error message noted above on quicksaves, on saving over previous named saves, and even occasionally on autosaves.

As before, the saved files seem to actually be there and be okay, because I can load them... just that the error message is disturbing to see every time, and has to be cleared by checking OK in order to continue.