As @ClockworkOcean said, use a tri-planar projection method instead of relying on the landscape UV. Basically, you project the texture from 3 different axis (X,Y,Z) onto the object rather than just one (Z).
It worked fine, until I tried it on a rounded cliff:
So I don’t know what I missed here, you can see on the picture there are 3 different results (of course with the same layer painting).
The green area is acting pretty good.
The yellow area has normal problem and render is different, but still no stretching.
The red is stretched, but, when I sculpt this side of the mountain with a 0.0001 strenght brush, it fixes the stretching and the result is same as the green area. I thought of a refresh issue but recompiling shaders or restarting unreal does’t fix it, only tiny sculpt does… weird…