Decal smoothness slider not working

Decals remain highly reflective on all material presets, problem isolated to smoothness slider not affecting appearance of decals.

Problem persists with all vinyls, on all cars, on all graphical settings.

I've tried reinstalling the game, repairing it, and deleting savedata under My Documents, with no results.

Painting the basecoat works fine, smoothness slider works properly on that.

My PC meets system requirements, and all of my drivers are updated.

Included screenshots are of the chrome, metallic and matte preset, respectively.

Decal is gray, base is blue.