Yeah I’ve had this occasionally and I have a pretty big Asus 32" widescreen monitor.
It’s an easy fix. Make sure you reset the WMR VR environment every now and again. Also make sure there is enough light in the room, but it doesn’t directly shine into the cameras and for the monitor it’s usually fine for the WMR Portal, stop the mirror and move the MSFS mirror off to one side.
I know this is a pain but you kind of get used to it, and it becomes second nature after a while.