tag selector does not work in LAN-MP

This is a bit complicated to explain, but I'll try my best.
When opening a World to LAN, tag selectors no longer seem to work in commandblocks. I have the command

/testfor @e[tag=isCheating]

in a CommandBlock with

/stats block x y z set AffectedEntities @a PCC

In singelplayer using dummy ArmorStands everything behaves as expected but when opening to LAN every cokmmandblock using the tag selector seems no longer to work.
It's very weird.