OK, I think I've got a working example of the delay from one of our testers' saves, but it probably wouldn't hurt to have more, since it seems to be happening very inconsistently (the one I have took five tries to get the slowdown.) So if anyone seeing it could upload the save where it happened (
instructions here) and let me know here, it may help us figure this out faster.
Just to be clear: what I'm looking for is saves that, as described above, seem to freeze up but eventually start moving again, at apparently random dates in the game.