Help Phone never sleeps, wakes on touch

[MistralNight]

Myself and a friend both got Unbranded HTC Desire Z's at the same time, a week ago.

Mine works perfectly, but my friend's doesn't seem to ever go into sleep mode.

On mine if you press the power button, the only way to wake it up is to press the power button again, which according to the manual is the normal behaviour. However my friend's screen still responds to touch, and will therefore wake constantly in his pocket, draining his phone in a matter of hours. Also the 4 softkeys at the bottom will activate the screen.

I have scoured the phone for an option that could cause this, and googled for anything that could prevent the phone from sleeping, or "wake on touch". I've tried programs that remove the screenlock, and a program which changes the "wakeup" key to the trackpad, and also task killers and disabling services. Also "Spare Parts" tells me that time without sleeping is 95%, over 2 hours unplugged.
As a last resort I just tried a factory reset, and the problem persists. It is an unrooted, unbranded, HTC Desire Z. I am at a loss guys, has anyone else ever experienced this or know what could cause this?

I'm thinking of sending it back to the manufacturer

 

[Stuntman]

Sounds like a defect with your friend's phone. What happens when your friend presses the power button. It should just lock the screen.

 

[MistralNight]

Sounds like a defect with your friend's phone. What happens when your friend presses the power button. It should just lock the screen.

If the screen is on, pressing the power button turns off the screen. But then touching the screen turns it on again, with screenlock enabled. Still havent found a cause

 

[dotzev]

"If you go into Settings > Applications > Development there is a setting for Stay Wake which is described as "Screen will never sleep while charging"."

Could this be the problem?