(This happens for me in Singleplayer; I add this note as it seems that Searge specifically needs it happening not on SMP but Singleplayer)

I started up my Bug Testworld in 1.10.1 and crashed.
This happens each time I open up the world in 1.10.1.
It does NOT crash if I open the world in 1.10.

"Description: Server forgot to send required information to construct BlockEntity"

"BlockEntity missing instance data"

BlockState: minecraft:command_block[conditional=false,facing=north]
Block coordinates: World: (18,65,32), Chunk: (at 2,4,0 in 1,2; contains blocks 16,0,32 to 31,255,47), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)

To verify that the CB it points at is NOT (or not solely?) the reason for it, I deleted the CB in 1.10, reopened the worldsave again in 1.10.1 and got a crash again, this time:

BlockState: minecraft:command_block[conditional=false,facing=east]
Block coordinates: World: (39,65,53), Chunk: (at 7,4,5 in 2,3; contains blocks 32,0,48 to 47,255,63), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
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Edit 1: Just saw that Searge requested for it: https://twitter.com/SeargeDP/status/745602435612282880
Edit 2: Provided a world download for him/link is sent.