the engine clear isnt bug proof either. I used it and went to the example you gave which sorted me. Also, I figured out why I was having access errors:

Make sure your sprite is being killed before it is allowed to execute a domove event.

Let me explain

In my pong game, I kill all 3 sprites when a round is over then a new round begins they are recreated. If your sprite is killed and then domove is being run it is no longer available and will show an access error. It will usually happen if you have sprites being created right after being killed.

To fix make sure you call Spriteengine.dead; DIRECTLY AFTER killing sprites (force it to be used immediately following destroy of sprites). This will make sure dead is updated before the move section.

Also place Spriteengine.dead; ABOVE your Spriteengine.move; in your timer.