Power button not working won't stay on.

Ok, so I bought this switch and it had a busted left joy stick and power button not working. But it was powered on and I could put a game in it okay games and even wake up from sleep mode with home button.

Took it home and I did a factory reset on it.

It sat for 3ish days.. I came back to it turned it on (via pluging it in power button broke)

It started up then when it got to the home screen it went black ( power off)

Tried once more same thing..

OK. So I do a hard reset on it ( plug in and hold + & - volume)

The switch boots up and stays on. I can go through menu's and such no issue. So I factory reset.

( long story short it repeated)

Once at home screen power off..

I then replaced the analogs ( broken)

Applied new thermal past.

Then replace power ribbon cable.

Still did not stay on...

I don't know. Help please?