Hi @eyetrackjack thanks for your patience whilst we tried to have a look at your project intentions. After consulting, I am afraid that it is not clear as to the best means to approach this multiple WPF windows format you are using.
Indeed, WPF with multiple windows in general applications is not a simple affair (as discovered from a cursory glance online) and as this is a rather unusual methodology, no in-house testing using the Tobii SDK has been performed in this setup so we cannot guarantee that all will work properly. It seems you already discovered some unusual behaviours in this regard!
Accordingly, we must recommend that you try to find a solution to your project needs that only require a singular WPF window. If you would care to share the project on Github, it would be helpful but I am afraid that for the time being, we cannot offer support for multiple WPF windows using the Core SDK.
Apologies for any inconvenience and thanks for your understanding.