Default Hardware problem?

Hi sorry for my English.
I have from july a nexus 7 WiFi 32gb with 4.4.4
At the start of august Power button didn't get off the screen. And Not appeared always the power popup.

I tried to reset But Not solved.

I send to rma.

It turn back with 4.4.2 and after 5 days some problem.

I downgraded 4.4.2 from 4.4.4 but some problem.
The power popup starts to appear random.

I send to rma and ask to change device

What do You think about this problem?
I didn't see thread of this problem.
Do You think asus will change my device?

Inviato dal mio GT-I9505 con Tapatalk 4