Ragman - Are the tracks moving, and it just seems like it is slipping while trying to climb back to the shallow end? If so, it could be that the bag needs to be cleaned. Mine would do that after about a half hour of cleaning when I first opened the pool in the spring. It could be full, or partially full. The bag pores also get clogged quickly which cuts down on the water flow, thus suction to create traction on the slopes. So, I would be cleaning my bag many times during my intital cleaning after opening. After the first spring cleaning it can run for hours before cleaning out the bag. It's been like this every year.