Sorry to hear about the brake issue.
About 18 months ago I also had the “Brake servo restricted. You can continue driving. Please contact workshop” message. I took the car to my local Audi dealer who were fully aware of the problem - it seems the sensor going wrong is fairly common and it would be fixed under warranty.
They did ask me how long I had driven the car with the fault. They said the fault message wasn’t correct and that you can only press the brake pedal a certain number of times before the “ABS module” gets “wrecked”. Fortunately, I had only driven about 10 miles so all was fine once the sensor was replaced.
However, it seems you perhaps drove your car for some weeks with the sensor fault. If you have changed pads and discs many times and the brake shaking fault comes back it would seem unlikely they are the cause of the fault.
In view of extended driving time with the original sensor fault might I suggest that the ABS module is looked at - maybe a different option to changing pads and discs yet again?
