Yeah, I was looking at the cdn, didn’t notice you had another version below 
Google for ‘collision sticking site:html5gamedevs.com’. It’s a recurring problem. The more contact there is, the more chance of sticking obviously. So box/box is full contact, even worse when they are multiple pixels inside each other, and the engine does not know how to separate them.That’s why a Circle usually works better, because the point of contact is much smaller.
Nice game btw