You are not alone.
My 2012 Alpha G2 drive has a similar issue. (20 Years newer.)
The Drive is removed for the winter.
The Left/Port Cylinder slowly extends itself over the course of a few weeks.
Since October it has extended 5 inches. (Not a recent picture.)
What makes even less sense....
If I reinstall the battery and then extend the cylinders a few inches, both cylinders extend as expected.
If I then retract the cylinders, when the Starboard cylinder bottoms out, the Port cylinder stops retracting. ???
This makes no sense as they are fed from a common manifold!
If I then extend the cylinders, when the longer Port cylinder reaches maximum extension, the shorter starboard cylinder continues to extend at double the normal speed, as expected. Both cylinders are then at equal, full extension.
Retracting the cylinders will cause both cylinders to retract fully, as expected.
I have retracted both cylinders fully and continued operating the trim pump to purge any suspected air in the cylinder to circulate past the cylinders overpressure valve with no effect.
In any event, I would expect an air bubble to expand and contract with temperature changes, causing the the cylinder to `Breath' slightly, not continuously extend.
And there is not a drop of leakage or seepage anywhere.
I have never noticed the cylinders extending while the drive was installed. I will have to look closer this summer.
My single cylinder extends about an inch a month.
Are you getting 2 inches a month from both cylinders?
It should be OK now. GA_B.