iPhone 8 Home Button Really Sensitive

Hi,

I bought an iPhone 8 yesterday from gumtree, and the home button is extremely sensitive. If I touch it as if I was using Touch ID it ‘presses’ the button really quickly for as long as I hold it there. It thinks a light tap is a hard home button press.

I can use it to go home if I tap REALLY lightly. Touch ID still works.

Research shows it could be a couple things;

 - U10 Chip?

 - Bent flex cable

- Bad replacement screen

I have tried changing the tightness of the screw underneath the home button, which does nothing.

Thanks for the help