Won't power on. Power cycle

Had 2 iPhone 4s'. One had water damage and would boot to the apple logo and reboot. The other had a bent frame. So, I decided to take the logic board from the working/bent frame 4s and move it to the good frame 4S using the non water damaged phone's battery.

Didn't work.

It would only power on when plugged in.

So I slowly started moving over all components. Now it just power cycles at the Apple logo. I swapped all components from the good phone to the water damaged frame except for the front camera. (battery, charge port, loud speaker, headphone jack/buttons flex, ear speaker, new screen)

Not sure why it won't work. Can a water damaged phone's frame cause the phone to not work?!?

Been doing iPhone repair for 5+ years and I'm stumped.

Help.