Same exact problem with Opel Astra K and Huawei Mate 10 Pro, but problem got worse when I went to update the software to the Opel service.
Had R 4.0 IntelliLink version 1.12.5.2 for 1,5 year and after updating it about 2 weeks ago, it's version is IP34.5.1 (1.34.5.6). Also HW version is E2.
Before the update I had the random black screen on android auto, about 1 out of 4 times but it was working without issues 3 out of 4 times. After the update..... I ALWAYS get black screen
So, the problem got worst for some reason.
So, I completely factory reset both the phone and R 4.0 IntelliLink... unfortunately same issue with black screen. I also tried both original cable and an SBS type C cable that used to work before the update... nothing again..
I also have a Lenovo Phab that works without any issue on Android Auto! Also iPhone with CarPlay works very nice and always as well!
Tried everything I found on the web regarding dev mode etc but nothing helped. The screen remains black, understands the touch and in order for the screen to show R 4.0 IntelliLink default icons, I remove the key, open the door, lock the car and after 2 minutes I unlock the car, put the key on the ignition and everything is back to normal.
Really don't know why exactly the problem got worse, although I read around the web that in order for Android Auto to work on R 4.0 IntelliLink EVERY TIME, you simply have to update the software on the OPEL service.