Evening again ,
the RX doesn't matter which servo you toss into it , but you need to find out if its the servo ( which is the first and easiest check to do )
Simply take the 1/4 scale and place it in the RX slot where the throttle goes ( usually number 2 ) and see if the 1/4 scale glitches , if not , then you know its not the RX or TX and something happened to the servo itself ( like maybe got a little wet ) . Then if this does not work , THEN you go on with the rest of the "process of elimination" steps to find it .

Good luck , cause sometimes glitches can be a PAIN[:@]

Oh , one more thing ... you say you shielded the throttle cable ... WHY ? what is it your using ? I use air line tubing from the auto parts store ( the stuff that you use for cars air shocks - it comes per foot and is around 12 cents per foot and is ONLY nylon/plastic mix and 1/32 stranded cable fits perfectly in it ( with no chance of glitching due to a metal liner )