Thank you for the response, but sadly, 17w45b didn't fix it. Are you able to replicate the problem?
Yes, but it doesn't say whether it fails on load. According to Dinnerbone: "Functions will be completely parsed & cached on load. This means if there's any command that isn't correct for whatever reason, you will know about it on load."
If the range is lowered to 1, the zombie isn't affected, elsewise it is. Targeting the zombie works correctly.
The zombie was in range in both cases as the entitydata affected it in both cases. Setting it to NoAI in the first command block doesn't change anything besides the zombie then not having an ai. I also tested this in multiple worlds and multiple locations. What do you mean with range?
I feel like an idiot - I checked for redstone sources but somehow missed the inverted daylight sensor that was right ontop of the command block. Still, there is the bug that the command block only executes when recieving a block if the redstone signal is there before the command block is placed, but that is already described in MC-63831. Can this bug report be deleted?
Just nitpicking - one character in the input box is enough if you then press a button while the text box is not focused 😉