It could be the shading effect of kodi interface (maybe not correctly managed by the video driver). Try to disable it in the screensaver configuration and check if it freezes. You can even try to access the config menu while playing movie to check if it's the shading effect.
Sadly I've tried disabling the screen saver completely.. still locks up. Also seems to happen within 20 seconds sometimes so it'll be way before the screen saver triggers.
Again.. if its doing something like playing a movie or a game.. I can leave it for hours with no freeze. But if it's idle and not doing anything.. it freezes.
Might be a power save related issue with the Nvidia drivers since it doesn't happen on batocera with nouveau. But they have an older Kodi so no Netflix add-on and no chrome... Can't win haha.