Boot loop caused by possible hardware issue?

I have an iPhone 7 plus that a person gave to me to repair. The person supplied their own screen (which I dont care for). I noticed right off that someone tried to repair the phone, because when I opened it the touch and lcd flex were torn and the camera flex was stretched. I replaced the screen and everything worked. It worked all night and I left it charging. The next morning it was still working just fine. I rebooted it several times to triple check everything. I always test calling, touch, camera etc. When I was driving to drop it off, it randomly rebooted, then went black then back to the apple logo. I tried to do a hard reset several times. Nothing worked. So, I tried to do an update and restore through itunes. I was still in a boot loop. So, then I started to work backwards. I unplugged the camera flex and it booted fine, but the home button wasnt working. When I plugged the camera flex back in, it boot loops. I go home to swap the camera flex with a new one. I get the same result. If I leave the camera flex unplugged, it boots. The home button at this point is non functional, so Im past that. I just want to know if this sounds like a board level issue at this point? Or maybe I should try another camera flex (I'd need to order one) to rule out having a bad original part and replacement part?

I know this was a lot of info. I hope I explained everything clearly.