I have the extended battery for my X. I was going to use the original back so I could use my innocase case with it. However when I put in the extended battery and put on the battery with the original back it causes a water mark type thing on the screen. it gets larger with pressing on the screen. When I take off the original gateau back it goes away. Now I know the way answer is stop using the stock battery back lol. But I am moe curious as to why it happens and if there is a way to fix it.