It could be the Tristar chip. Search YouTube for iPadRehab channel and watch a few of the Tristar or not charging videos to see why it may be the case.
This part can die when using non-genuine mains charger and/or non-genuine cable due to not filtering spikes on the charging lines if I remember right.
I presume using a white lightning port replacement on a phone with an existing black lightning port is fine?
The parts don’t identify themselves to the mainboard and be detected as a mismatch will they?
I removed the vibration sensor to pull the tabs at a better angle and the first one still snapped.
I removed the second adhesive strip without issue then I heated the phone from the bottom at 170C, without a nozzle, with my hot air station for a few minutes from a distance then I got a bit closer until I was satisfied it was warm but not scorching.
Then I used a pick on the outside (case edge, left side) of the battery and used the iFixit tweezerpressed together to slide behind the pick on the side I had already removed the strip from.
I was able then to grab the adhesive strip with the tweezers and subsequently pull again using my finger and thumb.
The battery will be free floating when the second strip comes out.
Thanks for the guide!