I changed to -20 and every 0.5 Seconds without problem. What Browser do you test it?
Try to disable the the destroy event (Line 8), now the objects will add up but maybe it helps to figure out if that's the problem.
Edit: I changed a litte bit, please have a look if it's know work better.
drive.google.com/uc
Up and Down-ArrowKeys for the Player.