There is clearly some sort of parasitic drain on your battery, which is why it goes dead. That drain could literally be ANY circuit in the vehicle. Many people with unknown drains just give up and put a battery tender on the vehicle.
These type of electrical problems are the absolute worst to diagnose. Good luck. May the Force be with you. I wish there was a better answer to give you.
This is a outright lie. In the US, the Magnuson-Moss Warranty Act and the Federal Trade Commission explicitly prohibit a manufacturer from voiding your warranty due to aftermarket parts unless they can prove that those aftermarket parts caused the failure.
The key here is that the burden of proof is on THEM, not you. You do not have any obligation to demonstrate a cause for the failure. It is entirely the responsibility of the manufacturer to prove that the failure was due to the aftermarket parts. Which will generally cost them more than just doing the repair.
