Of course... silly me.
Here is a sample , using the same entity, code and blocks as one of the game levels, where the problem occurs.
Within the zip, there's a JPG showing one of the stall spots.
You can move the mouse to move the camera, zoom in/out with the mouse scroll and press [space] to perform a pseudo-jump.
Just pass in the stall spot slowly, back and forward. With me, eventually (max 10-15 secs) the entity stalls.
Thanks a lot!