Nope, they were free to move. I've done in it several puzzles, I think it can be done in any puzzle. I remember doing it in level 16. Let me know if can't reproduce it and I'll try to explain it better or something.
I have reproduced the bug, I think. If I press a direction toward the robot and then hold a different direction as I'm moving towards it, the bonk wont occur and the player instead stops in front of the robot, then moves the direction being held without the bonk happening. Is this what you are referring to?