iPhone Flashlight only works if you tap the back of the phone

Hey guys so ive been working on a few phones, i switched over the housing and everything on a iPhone 5C and somthing weird happens. Everytime i try to use the Flashlight or camera with flash enabled i have to turn it on, an than litterally tap the back of the phone with my finger around where the LED flashlight is and it turns on. It almost seems like a loose connection of some sort, can anyone shed some light on this issue? Maybe a screw isent as tight as its suppose to be? A grounding issue? It seems like when i tap it the connection comes together and the light turns on