We have a Dolphin Oasis Z5 (very similar to the M500 and M400). I have tried all of the different positions on the handle floats, and still cannot seem to get it to climb our walls. It will go vertical, but just will not get off the floor. I have read a few other places that water chemistry and the robot's filters can also effect wall climbing, and have tried playing with those to no avail. I am thinking it may be that the pool is fiberglass and the sides are just too slick for it to grip? Just wondering if anyone has any other ideas.