Replica power button not making good contact

Hi,

I am trying to replace the metal power button on an iPhone 4, but upon installation the power button is not making good contact with the power flex. I have compared the original button and the replacement and there is a slight difference.

This pic shows what an original one looks like:

http://www.lunacommerce.com/2011-7012-th...

and a replacement looks like this:

http://www.case-parts.com/uploads/detail...

so you can see the first has some sort of spacer.

Now I tried to remove the spacer of the original with out luck please can someone advise me how to go about installing this new button.

(I also have similar problem with the volume button)

Thanks