RE: Servo mis-positioning
I think DMcQuin answered your question, WRONG SERVO ARMS!. It is important to not mix brands of servo arms unless you are 100% sure they are compatible. One other remote possibility is that the servo motor buried inside the servo is slipping in its mount. This a a very rare happening but remotely possible. Most modern ones are glued into place but some are just friction fit and some have a screw you need to tighten down to fix its position. I have seen one instance where the fault was in the transmitter. If the fault always occures only on one channel it is possible that the potentiometer on that stick position is slipping in its mount in the transmitter. If you have an oscilloscope, you can check that out yourself, just monitor the input to the servo being effected and make sure it is 1.5 milliseconds long with the transmitter stick and trim centered.