Help with random actions

i have three movieclips that i want to play randomly, one at a time. Right now its working except for that after a time it will stop, none of the mcs will play. its probably a small mistake ive made but i cant find it.
there is code on the keyframe, the empty mc, each of the 3 moving mcs and inside of them on the first, second and last keyframes.
i might be going completely the wrong way with this and if anyone has a better way of doing that would work as well.
thanks