Hey, checking in on this thread to see if anyone has found a solution to this problem?
I'm in the same exact boat, using a RPi 4b (8gb) connected to a US CRT with a fresh install of Kodi 21 and Fen Light.
I came from a RPi 3b with the exact same setup with this issue not present, but as soon as I moved to the Pi 4 the issue showed up.
I've dug through every setting and forum post imaginable, and I was unable to find a solution. Any assistance would be greatly appreciated, as it's just barely annoying enough to cause frustration haha.