Hi, have you used the retopogolize tool (which moves the vertices off a rigid XY grid). Perhaps accidentally? There’s currently a bug where that tool breaks grass placement. The ticket for that bug is UE-33064.
You could try the editor console command “RemoveLandscapeXYOffsets” which should remove any XY offset data, and then the “grass.flushcache” console command which will rebuild grass data.
Does doing that solve the issue?