Hi
I had this issue very occasionally on Nougat running on my Google Pixel C tablet which was usually fixed with a kill/restart of the Xeoma app but since upgrading to (stock) Oreo it's all the time.
When launching Xeoma I'm presented with this screen. You should be able to just make out my 4 camera feeds:
Only by accident while trying to get a screenshot of the issue for this post have I discovered that the issue is fixed by taking a screenshot!
Is this a known bug on Oreo ?