Having downloaded 2021.6, I find that I have an issue with my two screen PC set up. (project and bins in the left hand monitor, composer and timeline in the right hand monitor)
When playing, trimming or any function in the right hand monitor, without warning the left hand monitor/screen automatically becomes activated and any keyboard or screen functions in the right hand monitor/screen become inoperable. Only by clicking within the right hand monitor/screen will the left hand screen be deactivated and the function become operable. For instance. when playing and adding a keyboard 'in' point. This does not always work if the lft hand screen has aactivated. Or, having added an 'in' point via the keyboard before the left hand screen has automatically activated itself, but trying to enter an 'out' point on the keyboard or screen, this does not work if the left hand monitor/screen for some reason has automatically activated. Trimming becomes frustrating having to constantly deacctivate the left hand monitor by clicking in the right hand screen.
I have rebuilt all my settings, changed my tracker ball to a mouse, tried a USA keyboard rather than my UK keyboard but the fault sttill exists. I have not tried editing in just one monitor as this is not my way of working.
I use Windows 10 as my computer platform which, I believe, has the latest update.
I have been editing on Media Composer since 1992 so I am well versed with bugs and problems, but I have not met this problem before