This link will help with the info:
https://www.audiworld.com/forums/a4-b9-platform-discussion-212/starting-push-button-a4-b9-dead-battery-advance-audi-key-2948154/
As Magnet has said, don’t throw good money after bad.
logically, if the problem wasn’t there before the brakes were changed, and Audi have checked the suspension, it points to an issue with the fitting by the original garage.