Battery drains really quick after home button replacement

Hi Guys.

Just had an iPhone 6 returned to me i replaced the home button a couple of months ago & according to the client ever since i did the battery drains in less than 4 hours.

I used a genuine home button recycled from another iPhone 6 so its not a copy i have tested the battery with coconut battery app & its all working fine so it doesn't appear to be a battery issue.

I can't use the original home button as it was completely missing when it was brought into me so i can't test it that way.

Any ideas or anyone come across this before & did you manage to resolve it?

Thank you in advance.