No, I think it's a candidate - it's the second Mk 1 I've seen with "weird" behaviour, but had a seriously loose daughterboard. In this case, I did the same as the advice I gave for securing it as before - remove the original silicone bead from the connector header for the board, then make sure it's correctly positioned, and finally coat the connector area and board with lots of semi-rigid hot glue to make sure it doesn't move. I also put big blobs at the opposite side to fix the board to two capacitors sticking up, to make sure it was supported on more than just one side.

It seems to have fixed it: we spend about half an hour turning it on and off, rebooting, all the rest and it came up perfectly every time.