Default Power button don't switch screen off

I just recieved unlcoked version of XT1058. But I was amaizing that power button don't turn off the screen. Not only...if the time for display time out finish, the screen try to go black for a second and after this wake up again.
This make the telefone to wakeup on every 15 secconds as my time out is 15 s.

I cannot turn the screen off in any case.

The telephone is stock AT&T branded.

Any suggestions?