Hello,
After a certain snapshot of Minecraft update that took place in autumn 2023 (I don't remember the exact date), after loading the world map in the MCA selector, all the grass is rendered in black. I don't mean the dirt block with the grass still showing correctly, I mean the grass as a plant that has the id minecraft:grass_block . Whether short or tall, the grass plant is most often found in the plains and savannah biomes, and it is these biomes that are full of black dots on the map in MCA.

Steps to reproduce:

1. Open Minecraft Launcher.
2. Start a new game and create a new world in the survival mode.
3. Do some work in your world (build a house, plant some crops, make torches and place them around, etc.).
4. Close your game.
5. Install MCA selector 2.2.2
6. Launch MCA selector through file mcaselector-2.2.2.jar .
7. Open your saved world map in MCA selector. Maybe You may see black dots everywhere you expect grass plants.
8. If You do not see black dots, try to update your view. You should see most of them in the plains biomes.
   

I also had similar problem in history, but it fixed by updating MCA selector from version 1.17.3 to 2.2.2.
This similar problem also occured this way:
A new Minecraft snapshot was released. When i updated launcher to this snapshot, the problems with rendering world map appeared.
It also somehow messed with the proper rendering of the world, but I don't remember exactly how. I only remember that it was fixed by installing a new version of the MCA selector (2.2.2).

I use Linux Mint 21.2 Cinnamon 64bit
Minecraft Launcher Linux 5.15.0-91-generic 2.15.23
Game version 1.20.4 Java Edition