Son of a ##### there is some rust on the side of my receiver as well right under the plate. It's not pitted or anything so I'm not sure if it's worth worrying about but that's still a piss off.
from the first shipment nothing but the second same as you... sign of rust in the oil but no pitting.
now im wondering if i bought mine a few months from now, it would be pitted for sure. damn, luck i bought mine now.