You're on Win 10 right?
I don't have the same issue, I keep the main window on my 32" and 2nd on a widescreen 34 and it's sticky.
In Windows, which screen is set up as your main display? (Display Settings, then verify that the Make this my Main Display is checked under Multiple Displays when you've clicked on the 32" display graphic)
If it's not that I'm not sure ...