Having a lot of issues with pistons in 1.10.1, where they were fine in previous versions (map has been used since 1.9). Minecraft will crash, reporting the problem to be with a piston. Various configurations of pistons seem to do this, but especially when used multiple times (e.g. in, out, in, out, in fairly quick succession. Could share the map, though it is >100MB.
Reloading the map in 1.10 has no issues with the same pistons.