Hello Dave
Yes a pendulum swinging with a wobble results in a power-loss.
A loose, bent or otherwise mangled suspension spring will cause exactly what you are describing.
If the spring looks good then a loose fit between the chops would be suspect.
If that all checks out then another possibility would be a pendulum bob that is not hanging on the exact center-line of the wire leader. In other words the spot where the bob hangs on the hook must be on center with the wire above. If it is off center then a wobble will likely occur.
Best, Phil
