Single player world, created fresh in 10.0, now running 10.1, never modded. I was experimenting with the timing of a hopper loop involving a sticky piston / redstone block / normal piston by putting an increasing number of items into one of the hoppers while the timer was running. The game crashed, after turning sky-coloured for a moment, and I think it did so while extending the normal piston, but I cannot reproduce the error. Can't tell whether this is a new problem to 1.10.1 since I just created the machine – it ran "fine" (it's not working perfectly but that's likely my fault) for several days of in-game time. The world seems not affected by the crash, I can reopen it and play it normally. I saved a backup and can provide it if required.

I know, not very helpful, but I'll keep trying and come back to amend this if I can hunt it down. This might be a duplicate of MC-103981, but I am not certain because the behaviour is different, though the error message is the same.