IPhone 4S problems, troubleshooting repair?

I'm repairing a white iPhone 4S for one of my friends and so far I've gotten it to work EXCEPT for the LCD which previously, at first when I replaced it, it worked perfectly fine. I replaced the screen yesterday and then went back in to replace a proximity sensor/ power button flex cable, and the camera. Just my luck, the screen works when it wants to. Right now I have it working but with it flickering constantly (it's a lot less noticeable when the brightness is all the way down). The camera also is working fine BUT the flash doesn't work? If anyone could help me figure this out that would be great! If i could at least get some sort of parts layout diagram to see where each connection goes to that would be awesome, this way I could narrow down what the problem is.

Well it sounds like a loose wire. I would unscrew and take everything out again and replug everything back in. Make sure the everythig is hooked up appropriately. Here is a list of all the plugins and parts. Also comes with pics:
please vote best answer if fixes problems.