Does not matter if the faulty product is a RMA, if it's still under Warranty, faulty products can (by Law) be replaced/repaired/refunded depending on the Retailer/Manufacturer's policy. Logitech would normally replace because it is the cheapest possible solution, to repair may cost more than the production of the faulty item.
That's the main good point with Logitech, they usually replace without any quibble. I once had great problems with a SteelSeries Kinzu Mouse, the Retailer Listed the Kinzu with a "white Scrol Wheel" photo, what I received was mouse with a "Black Scroll Wheel". SteelSeries replied that they did not *Endorse this mouse and would replace it, after that exchange, I was totally ignored, even my Login on their website was erased. Contacted the Retailer, Overclockers.co.uk and also received much promised reply without any result. Basically OVERCLOCKERS.CO.UK & STEELSERIES "(should not have supplied the Retailer with an unendorsed product} "ripped me off", for the price of a mouse seems a joke.
ATM, I'm using a Logitch M310 and find it most suitable for my needs, tracking is amazing, kudos to the SetPoint 6.15.6
BTT. Maybe they'll send another different product for the second RMA.