I've found a bug with the command block. I was teleporting and i teleported myself to a coordinate. And i was teleported to a place where i teleported to another time. The chat says that i was teleported to 2 places. On the screen shot you see 2 coordinates. I teleported myself one time. On the other screenshot you see that i must teleported on the gold block. That is the first coordinate. On the tirth screenshot you see what is in the command block. This bug is in singleplayer.
It looks like you have a button directly on the command block, this way the command block next to it is activated as well.