Main Camera not working but works with FaceTime.

OK this is a strange one.

I have an iPad 4 wifi +3G which i'm refurbing.

I have transferred the Motherboard battery & other parts across to a different casing which is in excellent condition.

The casing from original was pretty beat up & very badly damaged in one of the corners but everything on it worked fine including both camera's.

This is something i have done many times before without any issues so i'm not someone who is attempting this for the first time.

Everything is working fine except for the main camera when i try to use the camera app it just stays black & i can't switch cameras to the front facing one.

Also i cannot get a camera to work with photo booth BUT both camera's work fine when using FaceTime !!!!???

I have tried different headphone jack logic boards both brand new & from known working iPads I've also tried different camera's again new & from working iPads yes they work fine when put back into the iPads they came from.

I have DFU restored & updated to IOS 8.1.1.

Any ideas guys any help or suggestions greatly appreciated.

Thank you.