so, i have the unicorn beetle case for my S9 (and my fiancee's S9 as well) and this oil slick thing happened between the plastic of the screen protector and the phone screen. Ive cleaned the inside with windex, professional strength spray foaming g;ass cleaner, 98% isopropyl rubbing alcohol, dawn dish soap and warm water, dawn and cold water etc etc etc, ive even used a hair dryer to get it fairly warm and to allow the air to help move any water molecules from any pits in the plastic. In short, ive done a ton to this [email protected] thing and it persists. My fiancees case is fine and the older kiddos case for the A8 he inherited from me is the same brand and a year older than my case and has zero problems. I work in an office and dont get the phone near grease ever, so im baffled about where the oily stuff is coming from.