Not original power-button does not work after replacement.

I have an iPhone 4 which had troubles with the powerbutton.

I changed the power-flex cable, but didn't help.

Looking at the original part which was there to start with, I see my replacement part has a different number.

Thinking this could be the source of the problem, after searching the web I couldn't find the original part-number. What to do now?

Original part: 821-1246-A

Replacement: 821-1034-B

I have tried muliple times to change the part, to outsource DOA-parts.