Default signal on AUX1-4 at flight battery connection?

I’m very new to ArduCopter/Pixhawk 2.1, so please forgive any ignorance. I am building custom retractable landing gear for a large multirotor. I am putting one leg on each of four motor arms, and driving that leg up and down with an Actuonix (was Firgelli) linear actuator. These are the L12, 6v 210:1 50mm length actuators designed as RC servos. I have the Pixhawk 2.1 with the latest ArduCopter installed. The landing gear is configured with linkage such that when the gear is down, the LA is fully retracted. As the LA extends, it raises/retracts the gear. I have SERVO9_FUNCTION set to 29 for landing gear, SERVO9 (AUX1) set to MIN=1000, MAX=2000, LGR_SERVO set to deploy to 1015, and retract to 1985. I also have the LDR_STARTUP set to 0 for no action at start-up. I am using RC CH7.

Everything is working exactly as I would expect it should, and switches behave as expected. Gear goes all the way up, and comes all the way down. The ONLY problem I am experiencing is when the flight battery is plugged in, there is some sort of signal on the white “S” line from the servo connections of the Pixhawk 2.1 that immediately fully extends the LA to the end of travel. I have tried both AUX1 and AUX2, and both behave the same. Once this happens, I can then flip the CH7 switch to cycle the gear, and it will then operate normally. However, since my physical linkage for the gear is such that the gear is DOWN when the LA is fully RETRACTED, starting up the multirotor causes the gear to come up and drop the MR on the camera.

This is not a function of the LA being powered on, as if I remove the white signal line from the 3-pin connector, leaving power connected, it does not do this.

I spoke with tech support at Actuonix, and they said they have had these reports from both drone builders and robotics enthusiasts who are controlling these RC LAs with Arduino units (ArduCopter is a form of Arduino control if I understand correctly?). No one has ever gotten back to them with anything that resolved this auto-extension at power-up.

I was wondering if there was any parameter that I’m missing that would stop this auto extension of the linear actuator at initial battery connection? I realize that a complete redesigning of the linkage so that the gear is down when the LA is extended, and up when the LA is retracted would resolve this, but that is a lot of redesign work, plus there is a definite plus to the gear being extended when the actuator is fully retracted (backdrive leverage force is pushing against an already retracted plunger). If the actuator is fully extended when the battery is connected, the actuator doesn’t move.

Any help would be VERY much appreciated.