its your collision points i had the same problem , then i read an article about how they had the same issues back in the 90s with 2d games , try adding more collision points have at-least 6 and shape them like a hexagon or octagon as best you can with a diamond like V shape at the bottom , think of it like this a ball will bounce and roll off objects better than a square , a square base and a square object will collide and jam more