UE5: landscape paint material index-0 still visible beneeth any other indexes?

Hi, when painting my landscape, I noticed that material index-0 is still faintly showing up at the same place as any other material index I paint. It is as if it is part of the background.

I tried using 0.0 falloff and tool strength 1.0 but it is still there like it is 10-20% applied.
UE5-painting-problem-1

How can I have it not showing up when I am painting with other index materials?

I am using text tiled images for the texture that I created myself until I find the proper texture images later.

Guys, please answer this question.