Android auto keeps forgetting that spotify is installed

[arndtinger]

For a couple of weeks, in most cases i get no option to play music via spotify. The only possibility to get it work is:

a. To reboot the phone before connecting to the car.

b. To "remind" AA that spotify is installed (via Apps for AA -> Playstore -> spotify -> open. Then closing both apps and restart android auto).

"b" obviously only works with the phone display.

But after a few minutes not using AA Spotify is gone from the audio options. This is extremely irritating when dropping of at e.g. a filling station leaving the phone in the car connected.

The really bitter thing is: THIS USED TO WORK FLAWLESSLY for over a year (in several cars). Now it doesn´t (in several cars, too) So what happened?

Both apps are up to date and installed from playstore. Uninstalling and reinstalling (first AA then spotify or vice versa) doesn´t help.

Phone ist OPPO R9 (German Version F1Plus) Android 5.1.

Can anybody please help?

Thanks in advance

Cheers

Arnd

EDIT: since I do not know, whether this is a spotify or android auto problem: here is the idential post @ google: https://productforums.google.com/forum/#!topic/android-auto/UJuku-oxu7A;context-place=forum/android-...