I have a new dolphin evolution X5. About 4 minutes into the cleaning cycle when the machine comes up to the side of the pool, it falls over backwards. This seems to cause air to be sucked up into it because after a couple of attempts to clean the wall and falling over, it begins floating and will not finish the cycle.
The bag is clean and without air as I carefully immersed the dolphin and made sure all the bubbles were out before beginning the cycle. (I have owned a dolphin previously and occasionally had it float when I did not get the air out.)