What all manufacturing defects to check when i buy a new Window phone (lumia 820 or 920)?

[Vibhor Agarwal]

A friend of mine recently purchased a Lumia 820 and found that during the call the screen turns black.
I found that this is a common problem.
check out Lumia 920 - black screen during phone call - Nokia Support Discussions

I want to know what all manufacturing defects I need to check when I purchase a new Lumia phone so that I can get it replaced if there is any. This is because dealers usually give replacement if any manufacturing defect or issue is reported by the buyer within 48 hrs or purchase.

Do we have a list of such issues.

 

[rimlover]

screen gap between body and case. i'm returning my 920 for that reason.

 

[Laura Knotek]

Moving to Windows Phone 8 forum, since this is a question about Windows Phone devices, not this website.