Landscape components randomly not responding to material updates (UE 5.3.2)

I have this problem when updating specular for multilayer material.

The relevant section for material:

This happens when using instance material as well as when using the material directly.
Updating tiles distribution for textures is propagated in all components though.

I guess it is not related to what is changed in material but to the landscape itself

The landscape is not nanite.

Am I doing something wrong or is it a bug ?