Nulala

Hi, i had the software update and a minor service done on my Audi A3 1.6 TDI on Thursday. On Sunday morning, the car wouldn't start and there was smoke coming from the engine. It was towed to the Audi dealership on Monday morning. They have been testing the car since trying to recreate the problem. They came back to me today saying there's a problem with the exhaust regulator valve. It would normally cost €1600 to fix but they're contributing €1100 so it will still cost me €500. The mechanic said it's a mechanical problem, not an electronic problem. I have had the car two years and have never had a single issue. I cannot believe that it is unrelated to the software update but do not know how to proceed from here or how to prove this? I wish I had never had the software update done, I had no idea it could cause these kinds of problems. I would appreciate any advice, thanks