iPhone XS Max randomly turns off after around 5min (Not Charging Port)

Hello,

I have an iPhone XS Max brought in by a customer that randomly turns off after 5min. I have looked at previous answers that have said the issue is the charging port however in the two cases I have, the iPhone has never been opened and thus the charging port is OEM, the same one that came out the box.

I have replaced the battery which worked for around a week before eventually reverting back to randomly turning off. I also have replaced the charging port just to check. I used another OEM one and the issue persists leading me to believe its the motherboard.

Upon inspecting the motherboard I haven’t found anything significant however maybe i’m looking in the wrong direction.

If anyone has had this issue before and fixed it please let me know! :-)