Help needed on stopping sprite movement

Hi all,

Cannot figure why this is happening , probably something simple I'm overlooking, but I have a infinite flyer type game and when the player hits block moving across the screen the player falls to floor. So I want all blocks to stop moving on screen and any spawned off screen to stop also. But randomly what I get is the blocks do stop, sometimes blocks carry on moving across the screen. How can I stop this.

Please check out my program CAPX