Originally Posted by Janke
You need to remove the entire sensor unit from inside the covers, otherwise you cannot screw out the original lens.
Also, it's very possible (probable?) the problem is the set screw was tightened so much that it deformed the threads slightly on the lens barrel, and they are jamming when the lens is turned in either direction and the deformed threads engage the good threads on the module. Mine did that. I was able to "re-form" the lens barrel threads enough by gradually turning it in and out with a very slight force when the threads jammed in each direction, repeated a number of times until the lens would unscrew from the module. Go slowly and don't try to do it all at once.