Some TVs store unique picture settings for each framerate/resolution.
What I mean by this is that I adjust the picture settings (on TV) to my preference when Kodi is outputting 1080p60. Now I play a movie and the Kodi output switches to 1080p24 ... all of a sudden the TV is using fresh picture settings. I must perform the adjustment once more. And also for 1080p30.
And the picture settings can include HDMI black level.
Perhaps this is not your issue, just a guess.