Only having used it once before I took the bottle of Meguiar's Scratch-X out of the trunk to buff out a scratch and literally water-consistency stuff just poured out of the bottle - normally it's a white paste. I shook it up well and still...watery and clear with tiny little white chunks. What gives? Will Meguiars replace this? Does this stuff have a limited shelf-life? (I bought it about 6 months ago).