Servo voltage inconsistency after upgrading/downgrading from 3.1.2 to 3.4 and back

Hi, sorry for the long initial posting.

I have 8 pixhawk 2s running rover on a gas operated boat. The throttle is controlled with a hitec pwm servo with no digital control.

When using fw 3.1.2 on a new, out of the box pixhawk, everything functions predictably. It is also worthy to point out that the servovoltage is 5 volts under this firmware. (which i think is where the future problems lie.)

When a pixhawk is upgraded to 3.2 or higher to take advantage of the vectored thrust parameters, the servo voltage goes to .04 volts. (if is possible to change this, then I am not finding it)

When an upgraded pixhawk is written to another platform, say copter, to erase firmware, and reflashed with the 3.1.2 firmware, the servo voltage problem persists. In this case, I assume there is a peripheral device onboard the pixhawk that is accessible from 3.2 and greater and automatically disables the servo rail voltage, and when rolling back firmware, this is not reset on the peripheral since the older firmware doesn’t have direct access.

The result is that both upgraded and rolled back firmwares cause erratic spikes in the mechanical servo physically driving the throttle on the combustion engine.

Finally a question… Is there a way to restore the peripheral behavior to the original factory setting? Once I roll back a device the servo rail voltage remains at .04 volts rather than the desired 5 volt baseline for the servo. Even with a BEC placed on the 5v and ground lines of an open aux port, the behavior persists, since I believe the servo output internal to the pixhawk is being latched at .04V instead of rectified to the 5v target.

Any help would be appreciated. Either with fixing the behavior on the 3.5 firmware or resetting the internal settings of the pixhawk back to factory in older firmware.

I’ve never heard of such a problem. can you post a flash log?

Sorry for having to link this…

I keep getting the following message when uploading to this forum, even though my log file size is 1316kb:
Sorry, that file is too big (maximum size is 4500kb). Why not upload your large file to a cloud sharing service, then share the link?