Flash and flashlight do not function but rear camera does.

I have an iPhone 6 at my shop that I replaced the display assembly and rear panel on (professional repair). The device had this issue prior to the rear panel replacement so the issue was not caused by me damaging the board. I have spent hours scouring the internet for a solution (I have restored, reset, and updated the device, l also tried three different back panels with three different power flex's as well as multiple different cameras).

The camera works completely fine, it takes photos with no issues, and when the flash is put on it acts as if it is taking a photo with a flash, however no flash is actually produced. The flashlight doesn't work either. There are literally no other issues with the phone except that it gets warm around the processor, I honestly don't know whether to call it abnormal, but it seems a bit hot for when its just starting up.

Since I have tried multiple flashes (one that I 100% know for certain works) as well as multiple cameras all of which work, as well as cleaned the connectors with isopropyl alcohol and reseated them to no avail I figure it is probably an issue on the logic board somewhere. I have looked around however and can't find anything that seems to suggest it and the phone to my knowledge was never repaired before this.

Would anyone have any clue as to what this issue would be? I've tried everything the internet has to suggest and have gotten nowhere.

TL;DR

iPhone 6, camera works but flash does not, neither does flashlight. Have tried multiple power button flex's and camera's and all software related fixes but nothing works. Assuming its a board based issue but cant find evidence of any, phone not water damaged. What could this be?