Bosch although I have not much information about the internals on Gen IV. I don´t know if it´s fixable or not.SO, if we had our time again, what motor battery combo/manufacturer would you go with?
Brose could be another option, may be the prefered. It´s prone to fails due to water ingress but it can be serviced, fails are mechanical, clutch and drive belt. Electronics are separated from mechanics