Making some test I discover also a ugly bug on the core software of the dial, if you add some custom app, as an example chrome, and then customize for chrome, after some time the app disappear form the list of customized apps, and there is no way to remove that customization or open to edit!!
I plan make usage of a direct contact I have on MS in the next hours to try to reach to surface team........
About monitors, this is great, I add a video card in the next hours to my main code computer in order to setup third monitor here and make exactly same test!
Hoppe I can reproduce here, if can , there is some chances to fix this issue.
Thanks so much for your effort and collaboration!! back soon with more info.