Bother cameras not working need HELP iPod touch 4

Bought an ipod with a busted screen off ebay. Replaced the screen everything works but the cameras (both). When I am on lock screen the little camera icon in the corner is lit up for some reason it also kinda sputters when on camera. It either freezes at the shutter or is just black. Not really sure what this could be... any ideas... I also replaced bother cameras...still nothing