Thank you for reaching out. We are not aware of any issues related to the use of multiple monitors and would not expect the number of monitors would have any impact on how the application runs unless the monitors are configured using different DPI's.
For the users experiencing the issue, could you please have them run our Sample Browser application and try to reproduce the issue with our "Simple IDE (external window)" sample? If the issue cannot be reproduced with our Sample Browser but is reproduced in your POC application, maybe you are missing an application manifest and/or declaration of support for per-monitor DPI (if your users have mixed DPI monitors)? You can see an example app manifest used by our Sample Browser here:
If you can reproduce the issue in our Sample Browser and the app manifest was not the issue in your POC application, can you please confirm the monitor configuration of the users with 3 monitors that are having issues? We would need to know the display resolution and scale (DPI) of each monitor as well as the physical orientation of the monitors (e.g., "monitor 1 is on the left, monitor 2 is immediately to the right of monitor 1, and monitor 3 is centered above both monitor 1 and 2") so we can try to reproduce what the users are describing. Additionally, is there anything else "special" about these third monitor configurations like customization of the taskbar or special widgets/toolbars that are "docked" to the edge of the screen?
