the cold could be the factor that is causing that.
i know many people use a cut up coke can or tin foil over the cooling head of the motor to help them warm up when driving them in the cold.
i wish redcat would fix the issue it has with stock servos. it seems to be the #1 thing to fail.
still, as you mentioned, replacements are cheap. and since redcat models cost less than others to start with, and the rest of the parts are good quality, they are still a good company IMO.
i had a backdraft 3.5, servo died on that to. i noticed the replacement they sent me was different. so, they may send you a different one as well?
none of the servos on my electric powered redcats have failled tho. still going strong.