Thanks Jake.
I went for a test flight yesterday to give it a test at low level (2000msl) since the last time I remember it working ok was relatively low and suspecting a static issue, I thought maybe at lower levels it just worked better. Nope, same problem of wandering and blowing through altitudes. Next step was going to go to ambient cabin for the static, although all of my other static instruments seem stable.
Got back to the hangar and ran a servo calibration/test and noticed it seemed to be slipping, but no slippage on the status page.
Engaged ALT Hold and went back to wiggle the elevator and could feel it slipping.
For some reason, it broke another shear screw without ever slipping on the Clutch.
I pulled the aft bulkhead out to get access to the servo and could feel some wobble in the control arm.
When I got the replacement screw 2 weeks ago, my partner in the plane installed it. I've been mending a broken shoulder and couldn't make some of the reaches. I guided him through the replacement, but didn't feel things myself. I think the castle nut may have been a touch too loose. I don't think he over tightened the shear screw, he was very careful.
I believe the shear screw broke on the very first flight after installing it. I guess I'll get a new one and then reinstall myself so that I can be confident that the castle nut is installed properly. I'll also turn the torque down from 70% to 40 or something small until I'm seeing slippage. My plane has pretty heavy springs on the pitch circuit, but the servo doesn't seem to have any problem moving them.
I don't have a picture of the servo handy. It's mounted on the pilot side, behind the aft bulkhead on the floor. Pushrod goes forward to a bellcrank to engage with the elevator pushrod.
I could move the pushrod connection on the servo to the inside hole, I don't need much throw in my plane, but since the clutch isn't slipping, I don't think that is the reason it broke.
Morgan