My world created prior to 1.18.0 is having a visual glitch an tries to generate new chunks over existing ones, ones I have built in. Luckily, it fails at doing so and goes away after leaving the game. One thing that causes the visual glitch is opening inventory too often. A sign of the visual glitch starting is the UI would randomly start blinking then the world goes into chaos if it continues after a minute.
I constantly have to go in and out of the game every couple minutes.