I recently upgraded monitors to new Dell Ultrasharp monitors from some older Dell monitors. I have 6 monitors, and two Nvidia GPUs to drive them all, and the old monitors all had DVI connections.
The new monitors though, do not have DVI connectors, so I hooked them all up by connected one Display cable to each GPU, to one monitor, and chained them across the two rows.
So basically, I have GPU 1, connected to monitor 1, monitor 1 connected to monitor 2, monitor 2 connected to monitor 3, and then GPU 2 connected to monitor 4, and so on. Not sure if this part makes a difference or not, but clearly something changed.
Now, whenever I lock my computer and leave for long enough that monitors turn themselves off, and then unlock my computer, it shuffles all my windows around randomly each time.
For example, everything I had in the top middle monitor went to the top left monitor, everything from the top left went to the top right, everything from the bottom left monitor got spread around to random screens, things that were corner snapped are now taking half of the screen, etc. Why on earth is it doing this?
There's this unanswered question about Windows 10 on the Windows forum https://answers.microsoft.com/en-us/windows/forum/windows_10-hardware-winpc/windows-10-multiple-display-windows-are-moved-and/2b9d5a18-45cc-4c50-b16e-fd95dbf27ff3 and there's another one that's been answered for Windows 7 in the same place https://answers.microsoft.com/en-us/windows/forum/windows_7-hardware/windows-7-movesresizes-windows-on-monitor-power/1653aafb-848b-464a-8c69-1a68fbd106aa?page=8&tm=1439182229675 (which also had a Stack Exchangelinking to it) but it doesn't seem applicable/the solution doesn't solve the issue on Windows 10.
Note: The monitors never change their orientation, or their arrangements relative to each other, e.g. my top left monitor always remains my top left monitor in the Windows display configuration, it's just the windows that get shuffled around.