Command block chains powered via redstone no longer function.
Everything was working fine in 16w41a, Update to 16w42a and only the first block executes. The redstone charge does not pass thru the block and into the placed repeater.
There is two examples. I will screenshot. First says @p just got a free Shulker Box, then clears all shulker boxes from their inventory, gives them a shulker box and finally clears all items on the ground.
Second, says 'Clearing ground items in 10sec. Then passes thru a series of repeaters for delay and finally clears ground items.
I'm aware this is well known, in the issue marked as duplicate Grum already responded, but I'd still like to mention that this behavior isn't limited to command blocks but applies to every solid block in the game (wool, bricks, prismarine, etc.).