Yuhang and Michael
We removed First Contact from the mirror and inspected the cleaning. It seems like some residue of the rubber stain remains and there is a lot of scattered light (fig 1 and 2).
After this we applied alcohol solution from a bottle in the ATC cleanroom (isopropanol based, I think it was called "Clarity" or something like that) in an attempt to remove water soluble stains (fig 3). Then after removing we reapplied First Contact.