Home Button suddenly harder to press?

OK, this is probably just an odd coincidence, but has anyone else having issues with the Home Button on iPad Mini (refurbished FD531LL/A) since the iOS 9.0.1 upgrade? Mine has suddenly become kind of squishy, forcing me to press harder to work. It still works but is not as crisp as it used to. I've had the unit for over two years - otherwise works flawlessly.Is there some kind of capacitance sensing under the Home Button that may have been altered by the iOS 9.0.1 upgrade? The unit was not dropped or mishandled at all.

I've done the Home Button calibration off a core App and the hard reset. Doesn't fix.

Thanks, Peter