Sometimes when a player plants the C4 on either of the two Execution maps, the C4 arms, and then falls through the map. The C4 then doesn’t explode, and the map runs until one team is killed, or the timer runs out. I have seen this happen on both maps, and I’m not sure of the exact steps that duplicates the issue. I have seen some players exploit this to lose the C4 out of the map (so some people know the exact steps).
Screenshots of the plant, and the disappearance (hard to catch, would be better on video):
http://images.akamai.steamusercontent.com/ugc/277347770291826679/9B9ED03CBB6B3C29BD9CD22EF7979A7E7BF449EA/
http://images.akamai.steamusercontent.com/ugc/277347770291826928/9D4B4F99A442FFF020C4905B19EBE06E618E7D7E/
http://images.akamai.steamusercontent.com/ugc/277347770291826997/CF63DCA645AA117AF49793663E9C02A20C827076/