All cameras failed after rebuild

Two times I recently rebuilt Galaxy S21 ultra phones which came from eBay with broken LCD's. I used the same OEM LCDs as I have for many phones. These two in succession tested fine with everything but the cameras. One solution proposed the 3 contacts near the battery connection may not have contact. I did have problems with a volume button and fixed it by pressing the NFC more tightly. I tried cameras from a previous tear down, Also didn't work.