I brought my Tower Trainer back out to investigate again why the elevator servo buzzs.

I built another pushrod, changed the connections from a basic nylon clevis to a L-connection. Still buzzing.

Then I found it . . . Whenever I move the elevator to the down position THE SERVO SHIFTS. It is fine when up but I can see the servo shift every time in down position.
The servo is screwed down all the way to the point where the grommet is impressed lightly and no more, so yes it is secure.

Why is the servo shifting only when the elevator is down and how can it be remedied?

Thank you