Why is my new ground material not updating, or letting me paint on the blank area?

Hi, bellow are two different pics of the two edited ground materials I am using. As you can see in one pic, the material is showing up perfectly, while in the other, parts of it isnt rendering at all, nor will it let me paint anything new on this area. When I test this out on a different scene, the material works perfectly. The way Im changing it is that Im using the pre-existing material, but re-0linking the grass in the layer blend. Is there any way to fix this problem? Thank you.

There is a limit to the number of different painted layers allowed in each terrain segment. I believe that the limit is 4 (due to 4 channels, RGBA).

Try painting over that entire segment with one material set to 1.0 and then try again

Edit: The reason why re-linking grass might be causing the issue is that you have 4 layers already on there, and adding the landscape grass node to your material counts causes the grass layer to count as two layers.