Camera Technical Question

Hope someone will have the answer to this but it's not an easy one

Have a 2014 Fiesta and I retrofit Sat Nav and genuine reverse camera, it worked perfectly

I have since changed out to an android head unit

If I use a normal reverse camera the picture is perfect, looks really good, however if I use the genuine camera for the moving reversing lines the picture is grainy and isn't great

What gives?

I thought maybe it was an NTSC/PAL issue but from what I've read the genuine camera is NTSC and the company I bought the head unit from say reversing cameras need to be NTSC

Is it something going on when the BCM adds the reversing lines to the camera? Or is it something to do with camera shielding?

I do remember having issues with the stock camera originally as I only connected the + and - video leads to the stock GPS screen but when I added the 3rd shielding wire the picture improved massively but being an aftermarket headunit it doesn't have anywhere for an extra shielding (I have tried just grounding it)

What happens in the standard screen with the shield attached? Why does it make so much difference? I'm wondering is this is my issue on the aftermarket head unit...