Grass Type does not show material for some meshes

Hello,

For some reason the material of some meshes in the Grass Type / paint layer in my landscape stopped displaying. It was Ok before. The related Meshes display correctly when opened in the mesh editor.

I tried rebuilding many things in the level but it did not help.

These vegetation meshes that started not showing are Megascans from Quixel:

Here we can clearly see the material displaying