The right rear leg quit--I figured a motor was cooked, but the problem turned out to be a stripped out plastic servo horn (note the bits of black plastic on the table).

I pulled the leg off to remove the old plastic horn.

The new aluminum horn fits the servo motor, but it's a bit dicey attaching the new horn to the 3d printed leg joint. It kind of works, but I'll have to redesign the joint and rework all the legs.

Changing two of these servo horns allowed enough control that I could attempt a sitting position.