Vauxhall Zafira popping from clutch pedal

Vauxhall zafira 2.0cdti Clutch DmF and master cylinder changed nearly 28k miles ago, car is 100k 2015/65 Driving the car is fine no issues acceleration and whilst changing gears. When I release the clutch pedal it comes up fine then there is a pop from the pedal can feel it and hear it. Pedal has always sqeaked before and after change. But this pop is new any ideas what would be causing it ? Thank you In advance