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#11
And in this latest screenshot, it looks as though a '4th' window could fit. I have no idea of what it could be, but it definitely looks like windows thinks there is an additional window and creates space for it. Have you examined task manager for any additional programs running? Have you tried WinKey+tab to scroll through running apps to see if there are 4 instead of 3 (i.e., one more window than what is displayed side by side)?
You may also want to examine Task Manager/processes to see if anything there could be interpreted as an additional window. Also, what about the SysTray? Anything running there? Try closing the programs running there one by one, clicking Side by Side on the taskbar after closing each one to see if it makes a difference.
James
Edit: And same for the 4 window shot...there's room for a 5th window. We may be onto something here...