James200

That link shows exactly what to do, and yes, it is the front calipers, apparently Audi knows about this. I used a wire brush that is used for cleaning pipe fittings before soldering to get all the crud out of the caliper, and really greased the bushing and where it installs in the caliper to try to keep the water out. The shake/wobble on my car was so severe I thought that people around me would notice!

I went through the same issue, I replaced the front discs twice, pads twice, and still got the vibration. I tried stepping hard on the brakes, my mechanic advised against that, he said the discs would heat distort and make it worse. The only solution was to change the bushings, it is easy to do, you can do it with the calipers on the car, just lift them off the carrier, a bit of manipulation, and then you can get the bushings out. To get them back in I used a clamp, the kind you squeeze with a pistol grip. This is WAY less expensive than changing discs and pads multiple times. The difference in friction between before and after on sliding the pins through the bushings was really significant.

This is the bushing pair for a 2016 A6 TDI

There is something else you need to look at. In Canada, corrosion is a severe issue, and putting a non-sieze compound on the wheel hub and disc face is standard good practice. However, the aluminum of the caliper corrodes around the bushings that the pins slide on, causing restriction to movement, so that the brake caliper does not move freely. This can cause you to chase an issue with the disc, and not find the solution. There are 2 bushings, you can knock them out, clean the caliper holes with a round wire brush, and install new bushings with lots of silicone grease. There is a soft bushing and a harder one, make sure you note which goes where.