Exchange texture from Child-Material

I have a parent-Material and created several child-materials for landscape tiles.

The parent material looks like this:


I then create the child materials like this

asset = AssetTools.create_asset("name", material_folder, unreal.MaterialInstanceConstant, unreal.MaterialInstanceConstantFactoryNew())
MaterialEditingLibrary.set_material_instance_parent(asset, base_material.get_asset()) # set parent material

To exchange the Texture (Base Color) of the child I do:

texture_asset = unreal.EditorAssetLibrary.find_asset_data( texture_path ).get_asset()
unreal.MaterialEditingLibrary.set_material_instance_texture_parameter_value(asset, "Base Color", texture_asset)

The problem is: The new Textures are not visible, when I assign the child Material to the Landcape Tiles. Always the parent-Texture (Base-Color) is used.
Does someone know what I’m doing wrong?
Do I maybe need to refresh something somewhere?

Thanks in advance!