Apologies for my appalling attempt at German. I contacted my mechanic and he performed 2 diagnostic scans. The first read 01423 lateral acceleration sensor (G200) problem in the electrical circuit (intermittent). He then replaced the sensor and recalibrated. The problem returned, so it was rescanned which gave the same code, 01423 lateral acceleration sensor, no plausible signal (intermittent).
The second scan was done at an Audi dealership and they informed him that they would need to replace the CPU, at significant cost, without guaranteeing that this would fix the problem. Brakes and ABS have been checked and deemed okay.