The mesh hit proxy (static and skeletal) store the section index as a material index. so the override material array need to be driven by the material index, not the section index. I will add the material index to the proxy data so the user can use the material index when dealing with material and section index when dealing with section
RESULT
The cloth section will be override
EXPECTED
The rubber section should be override
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-39952 in the post.