1980 BA-850 gearbox

The gearbox on my BA-850 no longer locks so the roof will not stay up without being propped with something. The gearbox used to make a ticking noise when cranking and is now quiet.

Is there something I can do to get it to lock again? I've seen diagrams pointing out the locking rod (protrudes near the crank rod) but I don't know if I can do anything with it.

Any advice would be appreciated, thanks.

after doing some research, it appears that this locking shaft turns to lock the lift system? Is this correct? My instruction sticker is too faded to read.