"Disable for fullscreen apps" looses display calibration.
With "Disable for fullscreen apps" enabled and during the day (colour set to 6500k), switching to a fullscreen app results in the display calibration for that monitor being lost and then reapplied after leaving the fullscreen app.
The same thing happens at night when flux is active - flux is disabled, and the colour calibration is also lost for the fullscreen app.
If flux is disabled globally (for an hour or until sunrise), the display calibration correctly remains for normal and fullscreen apps.
Edit: This happens on version 4.43 and 4.45.