If you are sure its motor related, i’d start by replacing the inductor first its the cheapest bit of motor circuit, but its difficult to diagnose without being able to test the product, the 3 phase motor can be tested by a meter to check the circuit is ok or not.
How do you diagnose a controller fault? I have a similar problem with a beko, turns on and fill up then complete electricity loss at the point it should start to turn the drum and heat the water. Works ok on a cold wash though, changed the element but that hasn’t made any difference so now I’m thinking the control board.