Home button not working, shorting contacts works sometimes

I recently replaced both the battery and the lighting connector assembly. Everything works fine except for the home button. I am still using the OEM home button assembly and the contacts are still correctly attached to the back of the digitizer. It appears that they come into contact with the metal prongs on the lightning assembly but the home button doesn't activate. I then removed the screen and tried shorting the contacts but nothing resulted from it. However, and this is what confuses me, if I hooked a paper clip under one and pressed it against the other and jiggled it around a little the connection was made and a home button press was triggered. I then removed the home button from the display and touched the contacts agaianst the metal prongs and depressed the button, again nothing, I tried again this time pressing down on the conctacts, firmly, untill they were fully depressed. This time, the home button worked and reliably too. So my question is, what is faulty... and how do I fix it?