Traduzione in corso passo 36
Success!! by removing the small black gear in the previous photos, I was able to manually spin the big brass gear to extend & retract the lens.
Upon closer inspection I found some sand or grit in the black gear - it must have been jamming the geartrain, causing the E18 error.
With the gears cleaned, I could reassemble and test the camera. No more E18 error - the lens extended and retracted again normally.