Cause: not holding the left/right directional key for long enough. (IE less than a frame after entering a teleporter) This causes igor to appear in the middle of the teleporter, and if you hold one direction key, you go in that direction.
_
1____..___...__..__
__..__..___...__..__
__________..______
.......______|______
...|_______......___1
.....__________|
(Yay for crappy ASCII of levels!)
Key:
. = empty space
_ = floor
1 = teleporter.
At the bottom 1 if you hit it and release right the moment you touch the teleporter, you can press left and hit the wall, and because MT put a bit of codeing in that stops igor from teleporting unless he has completly emerged from the teleporter, you can't teleport untill you go out of it.