Taskbar shows over video when focus goes to other monitor

Can you try disabling the notification option and check whether it helps on your scenario.

1. Right click the taskbar
2. Select Properties
3. Click the 'Customize' button in the section labeled 'Notification area'
4. Find the suspect program (Action Center, in my case)
5. Click the drop-down next to the icon of the offending program
6. Select the "Hide icon and notifications" option
7. Click 'OK' to close the Notification Customization screen
8. Click 'OK' to close the Taskbar properties menu

Hope this helps