It's amazing to see that the shaft into which the sidewheel screws is only 2mm thick, and actually thins where it meets the main unit. Almost looks like it's designed to snap?
A word of warning to anyone else reading this who's considering stripping their Nikko down:
It appears that Nikko are now using a heavy duty threadlock on the brass screw and disc(with the two holes) so any atempt to remove is likely to snap the main shaft they screw into.
I'm hoping Aralidte (no sniggers Glyn) will sort as a temp fix.