I have put this fix in here before, but here it is again:
Remove the latch from the top .
Take it apart.
Take the little tab part that moves to lock the latch inplace and drill a hole in the face that contactes the main locking tab.
Drill and tap it for a 5-40 screw.
Screw a round head 5-40 screw into that little tab.
Put the latch back together. Put it back on the top and it will lock every time.
The guts of the latch streach over time and so they do not interfear like they should. Some of the 200o and on latches were just made with too much clearance.
I had to rework the latches on my 2003 LS because they wouldn't lock.
Bruce Bing '03 LS