Joshua Gerrity

I've tested and verified that this issue doesn't occur when a command block chain removes its own power. The issue has to do with one command block chain influencing another (where a command block chain is defined as any number of connected chain command blocks, and the impulse or repeating command block that "chain" powers them, for lack of a better word).

I would guess, then, that this a coming feature?

/execute if fluid [X] [Y] [Z] minecraft:flowing_water

(I greatly appreciate the changes Mojang has made to the command block system, by the way. It is so much more efficient and concise.)