Setblock clocks, that is, the ones that use /setblock ~1 ~ ~ redstone_block and /setblock ~ ~ ~1 air, appear to no longer work in the latest snapshot(s). I'll place the redstone block, and only the air block activates. However, the one that uses /setblock ~1 ~ ~ redstone_block 0 destroy still works, but it's not the best option as it makes massive amounts of redstone block items.