I tried what you suggested by modifying roughness and metallic attributes. However, no matter how I modify them decals look same. In addition, I created a new deferred decal material to see if it was something in my decal. I just made a royal color only tied to base color on decal material. I still experience same problem. I also tried to change floor to same material that is on outside of building but it didn’t help either. This problem happens anywhere inside of my building and on multiple materials. I also tried to turn up radius of my pointlight in room. Attached is a photo of decal showing same issue.
