This also happens when hitting the stand up key, but is less pronounced due to less transitions in between.
While it's good that the player isn't frozen in place and has the ability to move, there should be proper transitioning animations for this kind of movement. Preventing movement what is now a slide, would be a bad solution.
Video with keyboard actions annotations here: http://www.youtube.com/watch?v=cfHF7GybZrU
Some key binds are different from the default ones.