Faulty spawn point with LandscapeGrassOutput

I use World Composition and have created some landscape tiles in size of 1009x1009 with a scaling of 100 for every three axis. All tiles of my landscape can be sculpted by the landscape tool over all tiles.

Now I have a material with a Grass Output and it’s grayscale value. But it dosen’t work properly. I think, the best way ist to look at the screenshot.

You see, the grass stops at the border between two tiles. Of course, I can sculpt over this edge without any problems. The next issue is, it’s a black area ( Value == 0 ). There shouldn’t be any grass there. I put in the Grass Mask in the Base Color of my material.

I already tried the two console commands RemoveLandscapeXYOffset and grass.FlushCach. Didn’t work.

I don’t know it is relevant. But this edge is exactly on the zero line from the world x axis. Above 0 there is grass, and below 0 there is no grass.

It’s look like that the grass mask isn’t recompiled after editing the material. Is there a way to force the Editor to rebuild all grass spawn points?