Cub 4 drop-feed lever still stuck!?

Many thanks for your reply, Ken.
I've taken off the bottom and think I see the spindle (a short grey cone-shaped thing, leading through a couple of grey tubes to the black bars that attach to the orange lever on the outside?). But no matter how much I press the bars or jiggle the lever, nothing's moving. I've added a couple of drops of oil where the rod passes through the grey tubes in the hope that might help but am wondering whether a well-aimed tap (to what? in which direction?) might be called for?