Android auto switching to Phone

I purchased premium abrp so I could use live data from my Opel grandland electric and the navigation via Android auto.

The live data works and abrp shows via Android auto. Unfortunately, when effectively starting a route, Android auto shuts down and the navigation starts on my phone. Then after a few seconds Android auto starts up again, followed by shutting down again. Thus goes on, untill I cancell the routeplanner on my phone. Please advice.