if it is board problem we wil ldefinately send you replacement part for fixing the issue, please email us for the problem, it is not motor problem, as I told you check the esc connections to make sure all wires are well connected and covered well by sleeves, and try to improve the esc heat dissapation by putting thermal paste under the heat sink.
If your ESC stop working or only one motor working, please open the enclosure up and checked the connections, reinsert the motor phase connections to ESC, 3 for each motor, and fully cover the connections with the sleeve. If your ESC get water coming in and stop working, power off the switch, try to use the hair drier to dry it up and reconnect it with the motor and switch it on again. If remote no longer control the esc, you need to charge the remote and go through the pairing process for remotes. Sometimes the ESC and remote can get reset and lose the pairing.