What voltage are you using as it may be a bit too low in torque? 2.6kg @ 6.6 volts. It could be a bit too fragile as well?

I'm using the JR DS362 which is 3.8kg @ 4.8 volts, but I'm using unregulated LiFe's which are 6.6 volts.

The push rod doesn't want to be too solid either. I use a 1/32" wire in a plastic tube that has a couple of mm's clearance on the wire. This allows it to flex instead of transferring the vibrations to the servo.