Different things, Audi garage won’t take it for another 3,4 weeks to even have a look at it. Some say it’s ECU but they’re not 100%, others that it could be gearbox dirty oil (but the gearbox was serviced recently) and then some that it’s just a sensor and to ignore it. But no one has had a look at the car (gearbox specialist) , all flat out for 3 weeks and won’t take it in.