Bafang mid drive czar prone to getting water into the controller, due to poor assembly. I most strongly recommend you get resistance metre and check the resistance from either side of the battery input to the frame of the bike is greater than 10 M ohms. If it is not there is probably water in the controller. If this is left it will destroy the controller. If caught in time usually nothing more than opening, drying it out possibly fitting a new gasket sealing it up and you're good to go, having saved yourself from a very expensive repair. Rodbick, I have a power electronics design engineering background.
