When Destructible meshes are hit or take damage, they always return the first Materials Physical Material instead of the Material that actually was hit. For many reasons it is crucial to have it return the correct Material.
For easy reproduction I have attached a example project.
If you open the “BugLevel” and hit play, you will see that both Materials are hit and return the “Destructible Damage Threshold Scale” value, which is always the value of the PM from the Material in Slot 0. (You can easily visualize it by exchanging the materials of the DM. The Traces are created inside the Level Blueprint.
I have literally spent months working around destructible and their bugs to get at least somewhat usable results, if at least this little bug can get fixed in a reasonable time, that would be great!