I've had my DFP for around 2 years now, put a decent amount of hours on them and they don't make that noise. I'd say send it back. Correct me if i'm wrong but aren't they the same pedals, DFP and DFGT?
You'd probably have to ship the whole product back, however, I'd first contact the retailer you bought it from. Your contract is with them, if they've sold you faulty goods, then they are your first port of call, not Logitech.