Voice control with Audi MMI not working after upgrading to 12.3.1 - not Carplay

Hello community,

since upgrading my iPhone 8 to iOS 12.3.1 I cannot use the voice control in my 2018 Audi A6 (MMI+) anymore.

I am not using Carplay. I use the possibility to tap and hold the voice control button on the steering wheel to start Siri (a car symbol appears on the iPhone´s display).

The phone still reacts to this but in the same moment the phone makes the sound that you can start speaking it stops the audio dialogue (often also with the corresponding sound). It seems that the iPhone does not connect fast enough to the cars audio as it did with last firmware. The same happens for example when trying to dictate a note (pushing the microphone key on the iPhones keyboard).

I already tried to delete the phone from the car and also the car from the phone - no change. This is very annoying because I really used this feature a lot.

Does anybody face the same problem? I think all VAG´s cars have to be affected (Seat, Skoda, VW) too. May anybody has a hint to get this working again?

BR Benjamin