Originally Posted by Dr.M
I should check mine. thanks for bringing it up.
I resoldered the motor wires on all of mine (the motor terminals have tiny holes for the wires so it's not as hard as it looked at first) and then entombed the logic board and motor terminals in hot glue. I put a blob on the bottom of the logic board to entomb the pot wires coming off then put the logic board back in and filled the top with glue, then put the case bottom back on and wiped off the excess. They should be ok for a week or two till the FBL upgrade parts come in. I might reuse them in a foam airplane because I don't think they'll have problems in the long run so long as they're not used in a high vibration environment.
My theory is that it's the weak solder connections to those tiny motor terminals that's causing trouble (the pot terminals and solder joints to the board don't seem that
bad but they're still delicate compared to the Coronas). Vibration weakens the solder joints over time and then the motor receives intermittent voltage when the servo is exposed to vibration which causes the servo to act more and more wonky as the motor is less and less able to properly turn the output shaft which progressively gets worse and worse till either the connection becomes so intermittent that the servo seems to go nuts or it just falls off and causes it to stop working.