Non-stop electrical issues after numerous checks and returns

As part of an insurance claim, my vehicle was sent to Audi Hatfield for repairs. After returning my vehicle for a 3rd time, as it was still giving EPC errors, the technician said it was due to a faulty thermostat sensor, which the insurance wouldn't cover as it's considered "wear and tear". I paid for the repairs and collected my car two days later. Now, barely 4 weeks later, the EPC errors are back, and the car is undrivable. I don't blame the dealership, I blame the manufacturer, as it seems they're unable to correctly troubleshoot and test their own products