Tuna

My A6 Allroad 2019 had alternator failure and was replaced by authorised Audi workshop. However, today they called me and reported a NOx sensor failure and quoted a 1200eur replacement cost. I had no problems with NOx sensor before alternator failed - so imho it is either caused by faulty alternator (should be covered by Audi) or workshop fault (should be covered by the workshop). Did anyone had similar experience and how it was resolved? (I googled this thoroughly and found that NOx sensor might need recalibration after power loss, but wad not able to get the information from the workshop did they perform such a procedure. ECU relearn procedure was apparently performed, as well as Drive Cycle after it). Big thanks to anyone spending their time answering to this question🙏🏼