Battery started to bulge inside the phone putting pressure on the LCD.
The guide was very handy. Be careful when using the suction cup and prying the screen from the iPhone body. The screen pops off very quickly and can easily rip right off the from the cables if you aren't careful. I also had an issue removing the bulging battery. I did have to use a hair drying on the back of the phone to soften the glue. The battery was still very difficult to remove even with the phone hot to the touch. The included screwdriver seemed like they were going to strip the screws so I used my own tiny screwdriver and it went much smoother. Also the plastic prying tool got really beat up trying to separate the LCD from the iPhone body. I took my time and went step by step. Had to resemble the iPhone twice when done as the new battery wasn't fitting perfect, but eventually got it to close like new.
Just don't force anything, whether it be removing tiny plugs, plugging things back in, or pushing the LCD back into the phone. Go slow, and be gentle when possible. It's very easy to break something with little force in these gadgets.