Fiesta ST Line brakes sound?

[Tezz Zilla]

Hi guys,

I have this issue with my Fiesta which I have picked up on for the last three days.

Whenever I come home from work, as I'm parallel parking I notice this strange sound coming from my brakes whenever I let go of the brake pedal. At first I thought I had rolled over some glass, at least that is what it sounds like. 

I tried to debunk it by turning hill assist off, because I thought maybe it was that disengaging. But no, it kept doing it.

It's not a constant grind noise, just the sound of what to me sounds like a piece of glass cracking whenever the brake pedal is let go.

Any ideas? :/