Landscape Material Grey Tile bug

Does anyone know the fix to material instances having grey block clearings for no given reason?
My material is smooth and constant everywhere but one part of the map… And i can paint over everything but this one part.
What is the fix? Is there a fix?

How many textures do you use for your material? -> also take a look at this thread: https://forums.unrealengine/showthread.php?50320-please-help-with-landscape-material :slight_smile: