[Skandalist]

I have "fixed" that problem just copying guisettings.xml from Kodi 17.4 (by the way, it doesn't need calibration). After that, calibration settings work properly even in Kodi 18.4 GUI. Maybe it is not necessary to copy the whole guisettings.xml, just resolutions section. Or, it is possible to copy resolutions section to advancedsettings.xml. I haven't tried that yet.

However, it is sad, that nobody cares about that bug...