Terrain splat maps using different textures cannot be modified in paint mode without ruining the splat info

Hi so i used world machine for my terrain and import the splat maps ect wiht 3 materials for red, green,blue , so i compile the shaders and put a layer infor in each terrain layer but when i want to paint over that for making small touches all the splat texture is ruined , but doesent happend with the modeling terrain part is only wiht the textures .

How can i achieve this make splat maps to have my terrain beautifull done and then be able to paint over that without ruining my splat info .

I appreciatte some help urgent.