While simulating a 390x390 round device (Venu 1) in the simulator there's a weird circle with red and white colors over it for unknown reason. I've uploaded the problem to the connect iq forum here: https://forums.garmin.com/developer/connect-iq/f/discussion/275194/red-circle-drawn-around-390x390-round-devices-in-the-simulator and I believe after the discussion that it is a problem with the simulator (sadly, I don't have any Venu 1 devices to test it on a real device). Anyways, here's a picture of it https://ibb.co/4ZZcnqT (kinda hard to see, but still there, look at the edges).
I hope that it will be fixed soon!