I have two texture layers in my terrain. When I paint the second layer on the base layer the results around some of the the joining areas will be like: 
I can remove it by carefully painting over it but in some cases it just grows further and consumes a lot of time and energy. I'm using Unity 2018.4.0f1 and have never seen such thing in older versions and 2019. However I have not used terrains very much. Tell me if you need any information in the comments. I have tried the following approaches:
- Disabling Alpha Channel in texture import settings
- Testing both color spaces (Linear and Gamma)
- Using the same texture for both layers (The white line still exists)
- Using custom Diffuse Material
The problem seems to be the generated SplatAlpha texture: 
As you can see four layers are generated: Red, Green and Black. But you can see the pixels I marked with blue and I don't know where are they coming from. Why is that and how to solve it?
