Boot loop after testing screens
New to posting on ifixit, but long time user of the site. I've noticed many people are getting boot loop issues at the moment and posting questions but none seem to relate to my issue.
I had a few old iPhone 6 screens laying around and decided to test them this evening to see if some could be recycled/upcycled. I tested around 8 screens and all was well, until suddenly I connected one which caused the phone to start boot looping, assuming it was just an issue with this specific screen I put the original screen on that I was using with the phone and expected everything to be back to normal...
No joy, I have tried two different batteries and also different screens, with and without the front camera flex connected as I understand this can sometimes cause problems, but its still boot looping.
The phone was running ios10 perfectly fine beforehand and in full working order. I have tried 3utools software however the phone does not even get recognised by my laptop when connected (official apple cable). The method I was using for testing was to connect a new screen, turn iphone on, test screen, if it was okay, turn iphone off via power button, if the screen was too broken (digitizer/lcd) I'd disconnect the battery to turn off the phone, the phone was always powered off when connecting the new screen.
Please advise as this issue is causing me great confusion, I dont understand how disconnecting and reconnecting a few screens could cause this.