Dretch is able to jump onto the slide and bhop/repeatedly jump to travel up it, but can't walk up the slide with wall walk. Also, once wall walk is enabled on the slide, the dretch is unable to jump
That surface is slick, and wall walk is meant to not work on slick surfaces. However, wall walking on slick surfaces preventing jumping is a bug that needs to be fixed.
Dretch is able to jump onto the slide and bhop/repeatedly jump to travel up it, but can't walk up the slide with wall walk. Also, once wall walk is enabled on the slide, the dretch is unable to jump