I'm making a pvp map and are using the snapshots to help me. I made a commandblock with the /testfor (and some other stuff) in it so i could detect when someone is on a certain block and when I updated to (I think) 14w8a so was the clock going slower. SEE VIDEO BELOW. (it may just be the command)

Link to bug: https://www.youtube.com/watch?v=ercr2s1GPNo&feature=c4-overview&list=UUUAmSMu5Do5uODRd1GgWbRQ.