Named 'None' in the material editor, TextureSampleParameter2d is not overridden in the material instance.
1) Create a new material
2) Add TextureSampleParameter2D, leave default name 'None'
3) Link it to base color
4) Save
5) Create a new material instance based on 1)
6) Open the material instance and check None in the Texture Parameter Values
7) Try change texture
8) Notice the texture is not changed.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-44577 in the post.