I am on the latest versions of VS (15.8.3), Xamarin etc. I am debugging on a Android 8.1 OnePlus6.
I find that I constantly need to delete my xamarin app from the device in order to be able to successfully build and debug the app from within Visual Studio.
It works the first time, but as soon as I stop and restart the debugger in VS I see the app started momentarily (Blank white screen) and then it just exits.
There are no errors reported on the phone or by Visual Studio.