In the newest 1.9 snapshots the command blocks are acting weird. When you first start to place command blocks and put commands in them they work fine. Then after a while or sometimes when you leave the commands will not work. It has been happening to me before this snapshot too and didn't think of it at first, but now it is annoying and frustrating.
Comments 4
That is not it. I have been in the spawn chucks (where my command blocks already are) the whole time.
If you move too far away, the chunks the command blocks are in will unload, meaning the command blocks are not loaded to run their commands. You can move them to the spawn chunks instead to keep them loaded.