Indesit washer motor problem

Customer thought belt had broke as she heard a bang and electrics tripped , motor was faulty making electrics trip when on a spin . Changed out motor for a second hand spare which I know to be working . All was good for first few minutes on a spin cycle then bang , motor flashed then tripped electrics . Any ideas I think a module fault but dont have a spare for that model to check . Thanks in advance . Heating element and all other components are testing fine .