What does this error sound mean?

I am unable to identify what these sounds mean.

What is disturbing is that at the end of these sounds it reboots and then ARMS ITSELF with Mission Planner reporting that it is DISARMED.

The kill switch will NOT disarm the aircraft.

I can not make this error happen, it just does. Occasionally I will get a normal boot.

No errors show on HUD, no errors reported in logs.

Firmware version is 3.3.3

Any help is welcome and appreciated!

Video is linked here.

The kill switch isn’t supposed to disarm the aircraft, only disable it from arming. It’s not a ‘kill’ switch. Just a safety switch that prevents the FC from sending PWM signal to the ESCs.

That first sound almost sounds like a reboot after an initial firmware flash or a firmware update. I think the second noise is the pre 3.3.3. ready tone? It’s been so long since I’ve had it though.

Under the existing pixhawk library of sound codes it sounds a lot like one of the I/O audibles but it is not an exact match.

I’m further puzzled by the fact that it begins the normal boot up sounds, then it gets cut off and plays the error tunes. If you listen close you’ll hear that.

We have had this error on another bird, the exact same one and we wound up replacing the autopilot. I’d like to understand the problem even if it means a replacement. If y’all think it would help I can send some logs.

I’m also considering re-flashing with the same version and see if that clears it, then try flashing to the latest firmware. But these two things still avoids the understanding of the problem so I’d rather you guys get a crack at it first.

Removing the kill switch does not fix the problem

Replacing the kill switch does not fix the problem

This error is truly intermittent

Formating the SD card has no effect
Reflashing with arduplane 3.7.1 has no effect
While arduplane 3.7.1 was loaded I did a RESET TO DEFAULT for the parameters, got a succesfull boot from the automatic reboot that resetting to default does
Next boot of pixhawk 1 has the error sounds, so reset to default did NOT fix it
Reflashed with Arducoptor 3.4.4.  Upon reboot error persists