when your switching these crystals around your not mixing a low band crystal with a high band reciever or vice versa are you.on my hitecs it doesnt matter you just worry about shift but it does matter on the 127 futabas.I had a similier problem with a flight pack.had 2 of them fully charged,measured 5. somthing volts.one would chatter servos,one wouldnt.i peeled the shrink wrap off the one and there was a little green spot of erosion on the solder joint but it read fully charged.how old are the packs in yout TXs.I had a battery in my kyosho TX do this once also,it was the series 91 air that uses 2-4.8s.