iPhone 7 plus is freezing after connecting front camera

Hi guys I need help.. I replace screen on my iPhone 7 Plus and after I complete my iPhone back I take a long time to boot up and after booting iPhone is very slow and on the screen is virtual home button. So I tried to found out what is wrong. And there is issue with front camera flex cable. Because if I connected flex cable with front camera iPhone is freezing. If I unplugged that flex iPhone is working fine and home button is working fine. So I tried to buy new flex cable and change it. But issu is same. So everything is working fine except front camera. Does anybody know how could I fix this issue? I repaired a lot of iPhones but I never saw this. Thank you