might also try recentering the magnet....or replacing the magnet if you suspect one side has a greater pull....
i know drac seems to have some sources for magnets,
otherwise, you can try the ones at radio shack,
they have the tiny neodymiums of about the same size
for 1.50 for two pieces...
they may be a little strong for the application though...
...
either way, careful of that spring when you take apart
the front end, i totally messed up mine,
and ended up breaking the spring trying to bend it back into shape...
took me 7 tries to find a piece of wire that would work....
most of the wires i tried were too stiff...
and now...sigh...after making a spring that works,
i think my magnets aren't centered!
too lazy to open it up again and reglue the magnets