Animation drawing at old location

URL of experiment: https://run.pavlovia.org/Am8302/shapecrush/html/
Description of the problem: Animation online

Hi
I’m using a really simple animation where a shape drops from top of the screen and the routine repeats. For some reason, when the routine starts again the shape flickers at the location of the last shape. I can’t work out why this would be as I have cleared the position of the shape at the end of the routine. Hopefully I’m missing something really obvious!
Cheers,
Alice