I also have this issue using GCM v4.6.4 on a Google Pixel 2 running Android 8.1.0 (build OPM2.171019.029.B1) when trying to access device settings on my Garmin Edge 1000. The GCM app crashes irrespective of whether or not the Edge 1000 is connected to my phone or not.
I also have a vivoactive3 registered in the app and this works fine
I am getting this problem too. It has only just started doing it and only on my Edge 810. My Vivoactive HR works fine. Live tracking no longer works either. I have emailed Support so now waiting for a solution
I have the same issue and also activity syncing isn't working properly any more since the update. I submitted a support ticket two weeks ago, had one reply and then the rep ignored all future emails.
As indicated by essexboyracer, the 4.7 update for GCM started rolling out yesterday and is now available to 100% of customers. This update resolves this issue.