I rebuilt the hubs on my 1009 about two weeks ago. The driver's side lock was acting like you describe it was loose, you could rattle it around but all the bolts were tight. And the passenger side didn't always unlock right away.
When I got it torn apart I realized that the previous person to turn a wrench on that hub had not reassembled it correctly. Inside the hub, past the lock there are two nuts separated by a washer. The innermost nut is the bearing adjustment nut it has a pin on it that should fit into one of many holes in the washer (washer has a key on it that keeps it in place on the spindle). Then the second nut goes on the outside and locks everything in place. There might be an exploded view in the TMs. I was working out of the Chilton's manual.
If the same person worked on yours the inner nut was never lined up properly so the pin would go into the hole on the washer. Overtime the pin was flattened, the hub assembly moved and the lock now has play.
I rebuilt everything from the spindle out when I did mine. Might have been over-kill but I now know what I've got. If you go this total rebuild route do not try to reuse the oil cup/bearing seal bad things happen.
Good Luck.