Need help with iPhone 7 Plus boot loop

Hi all, I’m doing a repair on a iPhone 7 Plus and it is now stuck in a boot loop. Now, I’ve had this problem before and it’s always been fixed by replacing the front assembly flex cable but now even after replacing that, it’s still doing the same thing. I’ve checked and it is starting properly when I don’t have the front assembly connected at all so I know my problem lies there. I’ve also checked it with two separate working ones so I honestly have no idea what the issue is. Any help would be appreciated.