Brake pedal switch noise?

[norfolkRX]

It's just started recently but doesn't happen all the time - when I release the brake pedal, there's a small single metallic ping noise.

It sounds to me a bit like a sticky microswitch or something similar.

I tried looking in the brake pedal area while releasing the brake pedal but of course the noise wouldn't show itself.

Does anyone know what it's likely to be?

Many thanks

[Jay762]

Not had that myself - car mat clear of lever? - if there is a spring as well, could it be that catching on something?