I have not tested the demo yet but I can confirm having similar problems in the past, in 3d or my sidescrolling game - which is why I changed all WED blocks from
to
so the player would not randomly get stuck at the x position when falling down. Obviously I doublechecked my code back then and figured it would be some precision problem with the collision detection and the block surfaces (and corresponding normals) in question.
As a workaround I chose a system which keeps the player's bounding box away from the walls (+ ground and ceiling) at all times but obviously this is a little harder to do in 3d (esp. on let's say 6 axis movement, like in a space fighting game).