Front Camera not working after back glass/charging port replacement

I’ve been repairing phones in my free time for a couple of years, but have never been as stuck as I am right now.

Client handed me an iPhone XS Max which had a completely shattered back glass, and which was restarting every few minutes.

• I replaced the back glass housing with a new original one, and after a number of hours troubleshooting, discovered that the reboots were being caused by the charging port which might have been damaged during the drop which caused the back glass to shatter, or by subsequent water damage, since large chunks of the glass were missing.
• After successfully replacing the entire back housing and charging port, the phone was not rebooting at all, and all problems seemed to be gone.
• Upon testing the phone post repair, I noticed that the front camera was not working, showing a black image. Please note that the Face ID sensor array seems to be working fine (unlocks phone every time, able to set up new face), rear camera works fine (in all camera and video modes), as well as the flash which works fine.
• Things I have tried till now to try and solve the issue:
  1. Hard rest
  2. Network/settings/all content reset
  3. Re-flashing iOS using 3uTools
  4. Carefully cleaning all flex cables and logic board connection ports using isopropyl alcohol and a small brush
  5. Replaced Face ID front camera array (in this case, both Face ID and front camera did not work - as expected since this was an aftermarket front camera array replacement)
• All the above measures have failed, and I’m on the verge of giving up and accepting that there must be some logic board damage(??)

Do you guys have any suggestions?

Thanks a lot!