I'm having an issue with my Dolphin Nautilus robotic pool cleaner. The unit turns on and starts to move but always gets stuck on the side of my rectangular pool. It would try to climb a side wall or stair, get up partially or all the way, then come down and turn to the side and become stuck. Attached are four photos of how the unit always ends up (usually after about 2 minutes of it being turned on). The unit was purchased last year and was used only for one season.