[hac_]

I do not think I am the first with this issue, as I have tried to read up on similar issues. But I have not seen many working fixes apart from shortcuts rather than stopping it happening.

Due to limitations with my AVR and 4K, I have had to use a DP to HDMI adapter to take Audio from my nVidia GTX 1050 to my AVR and Video straight to my TV. This has created many more issues than I thought not only with KODI but Explorer/Chrome and the likes minimizing to the other desktop, which does not exist, there are ways to get things back and or trying to make sure apps stay on the main desktop, but a lot of the time they seem to do what they want. I tried Ultramon which did help but it sometimes created issues and left me with a non functioning NVCP limited to 1080p.

KODI has been a real pain, at one point it all went away, I had my desktop and KODI at 2160p and everything was working well to a point and I had limited issues with KODI minimizing or jumping up to the top left corner, things like \\ helped get it back, but the only sure fire way I seem to have locked KODI down is to set my desktop at 2160p and 23 Mhz, this seems to stop KODI having a melt down, the strange thing is everything is upscaled to 2160p, so everything has to go into this resolution, but it was only the 4K UHD files that when exited would make KODI jump to a non existent desktop and sometimes I had to close KODI down from the taskbar to then restart.

KODI would also restore to the desktop a lot of the time saying keep new settings, it was as if it was changing resolution, but you have no idea what to, I thought if I locked the settings down this would stop it, but it had no effect, and the screen would bounce up and down to the taskbar or some other annoyance.

Anyone have any other ideas what to do here, as its really ruining the KODI experience for me right now.

Does not seem to be a driver issue as its common to old and new. I have set the 2nd non existant desktop to 800x600 which helps losing the mouse etc, but you cant just disable the 2nd desktop as you lose sound, if you go below 800x600 you lost HI-RES audio, what a mess

TV : Philips 65PUS6703
AVR : Yamaha RX-V477
Card : GeForce GTX 1050 2GB  - Drivers - 390.77
Windows 10 1809

I think the problem is most likely with nVidia driver and HDR-SDR switching that causes this. Not really a solution you were looking for, but I thought to point out that your extra display isn't really the root cause, it just causes some extra symptoms. Many of these problems occur also with a single display.

On my main HTPC (regular 1080p SDR output) I have a DVI-HDMI adapter for sound (with the phantom display), and I haven't seen any such jumpiness, Kodi stays fullscreen and sticks to the main display just fine.
My secondary setup with a 4k HDR TV doesn't have the separate sound and phantom display, but it still has jumpiness after playing HDR. Sometimes after stopping playback, the Kodi window moves to the upper left corner as a smaller window in some pseudo-fullscreen state. I'm also using DPI scaling on this machine, but I haven't bothered to investigate this more to see if changing that makes a difference.