Help with Rotating Sprites

I’m trying to program an enemy sprite to go back and forward between two blocks, I have looked at examples from other games and i’m 99% sure its the same code, however, when I run my program the enemy sprite gets to one of the blocks and then moves side to side instantly in the same spot forever. http://flowlab.io/game/view/556330 Here is my game and the buggy enemy.

Try changing the shape of the object, squares sometimes catch the corners of square floors, so that may be a possibility.