I have an issue that I'm sure is collider/physics related, but I'm not sure how to fix it.

In level 1 of the 2D game, near the beginning, you ride a platform up to the left to a small ledge with a cannon firing at you. My problem is that if a projectile hits me while I am on the ledge, it knocks me back against the level wall and I end up stuck to the wall, slowly sliding up. If I hit jump/rightarrow repeatedly very quickly, sometimes I can get loose, but usually I end up stuck and sliding clear to the top of the wall.

What could be causing this?