My enemies wont move after a bit

So in level one theres an enemy and he goes for ten seconds-ish before stopping. can anybody help me about this?
game https://flowlab.io/game/play/1150711

It’s just because of the physics,
no matter how long you make it, it will happen in the same spot.

Grazer explained it in another discussion:
http://forum.flowlab.io/discussion/comment/22930