Did you try programing a lower cut-off? If you program a lower cut-off and the cells are still dumping at that voltage you're going to need to talk to the manufacturer as it may be a battery defect..

Only other thing I can think of is temperature.. Have you checked temps on your motor an esc after the batteries dump? If they are too high it could be the heat causing the motor to loose power or the esc to do a safety shut-off..

Also, after the cells dump, see what happens if you let everything cool off and you plug them back in. Just hold the car in the air and see if it will give you normal power..