I don't see anything from what I can see of your code. I might be tempted to a sub-event on your System > BricksNumber = 0 of System > Trigger once while true, and place the System > Take snapshot of canvas... as an action under that sub-event. But I think that is kind of grasping at straws...
It's not one of those Doh! type things like the Snapshot sprite has it's Initial Visibility set to Invisible... or the Snapshot sprite is under a Layer that is set to Transparent No...