Ecu damage

Good morning.We sent an ecu to them for testing.Vehicle has intermittent starting issues.Customer drive vehicle into the workshop .Ford fig 1.4 tdci. they said there is a problem with the ecu. Customer reject qoute to repair .We get the ecu back and the vehicle have no starting after that.Seems the ecu is damaged further.Customer towed vehicle away.Took all his work away from our business. Last week we sent a ecu for a vw polo that have only idle issues.Customer drive it into the workshop.They claim ecu damage.Customer reject qoute.We fit ecu back in vehicle,now the vehicle is not starting.Cqn"t even diagnose the ecu.