Are you using a "collision box" for your player, or does your player sprite handle the collisions? Looks to me like your player sprite handles collisions itself, per pixel, which would have it's arm cling on to the platform when it's falling off of it - creating the problem you're having.
I use the "per pixel" method. Finally I found what was the problem:
I did use of a collision mask only for the first frame of the Idle animation. I pasted the same collision mask to all frames and for all animations. Now everything works fine.
BTW: the method described in the video below is not working for me (0.99.91)
After the "Copy Collision mask to each frame" operation, the collision mask of the HitBox is deleted and nothing happens to the other frames. I had to paste the collision mask manually to all frames