I have recently found dealing with warranty issues, they will lie and claim all kind of exclusions, especially if the failure is big and costly.
1) There are all kinds of exclusions in warranties they will try to evoke.
2) ANY modification can and will disqualify your claim (or be an excuse to deny you), no matter how unlikely that it was the reason for the failure. Slightly reducing the airflow made the transmission fail? There is a DSG oil cooler, but in most DSG cars there is also a thermostat to cut the oil cooler off in cold temps. It is a bogus claim, but now you have to prove them wrong (if your DSG has an issue).
3) If you don't have proof of maintenance, your warranty claim may be denied.
4) If something is not covered, like an accessory belt or hose fails, somehow causes damage to say engine or transmission, they may not cover the engine or trans.
5) You have to fight, threaten and in the end sue them. If you don't have an "expert witness" and lawyer in your corner, you might get run over by the auto manufacture or dealer, because they are after all the experts.