Volvo EVC Issue

Hi everyone. I have been experiencing erratic codes on my port driveline. My mechanic believes that I have a faulty EVC computer. I have EVC C1/C2 on D6 IPS 600s. He recommends that I change both my ECU and my PCU at the same time. I would rather only change one but he said that he cannot be sure which one is causing the problem and if we change out the wrong one, the faulty computer can damage the new one. I have attached a photo of the codes (which clearly mention the PCU) below. All insight and advice is greatly appreciated. Thank you!