OK. Did a bit of more debugging and I think I found the issue and a workaround:
- Re-installed SE
- took a vanilla backup of the common/SE folder
- launched (#1), worked! (btw, I can't seem to control my camera with the spacenavigator, i get into a constant spin)
-- now, I have 3x 4K monitors, so at this point I moved my main window to the middle monitor (SE opens on the left one which is the main windows display)
- exited SE
- launched again (#2), DIDN'T work
- removed \joy_3Dconnexion_KMJ_Emulator.cfg and \joy_SpaceNavigator.cfg
- launched again (#3), DIDN't work
- removed ALL config files (back to vanilla install)
- launched again (#4), SE opens on my main display on the left, DOES work! (we are on to something)
-- resized my window, but left SE on the left-hand side monitor
- launched again (#5), SE opens on main display on a resized window, WORKS!!!! (we are definitely on to something - definitely not the 3dconnexion suspicion)
- moved the window to middle monitor, still resized smaller, exited
- launched again (#6), SE opens now on middle monitor, DOESN'T work!!!!
- moved the "Non responding" window to left monitor (main), and closed SE
- launched again (#7), SE wants to open on middle monitor despite having moved it to the left one, DOES not work
- edited "main-user.cfg" and set WindowPosX/Y to 0
- launched again (#8), SE opens on (0,0) left monitor, and as expected it now WORKS!!
I repeated this a couple of times and I can guarantee now that when the position of my window is beyond the x-coordinate of my first monitor, things get nasty. My workaround is to move the window to my main display with an X coordinate between (0, 3840) in order to ensure the next time it will work.
Happy that I can still enjoy SE, but maybe something to be fixed here?