EPA mainly, that' the only one capable of causing issues (and abs).
It is possible the Rx is causing havoc, had one futaba rx from a friend that took out my beloved team orion 1308 when we were testing what's going on with his servos. if you have access to a multimeter check the lines, if the signal has around 3-4v it's normal so more than that (full voltage for example) isn't good.
Also, did the servos got hot? I would send the hitecs to hitec usa, the costumer service reviews here are tip top.