I had a locksmith look at my trailer lock. He removed the inner plate and tightened the screw Iowa Dave referred to. The locksmith said these locks were very common, and that others who have had this problem have put Locktite on those screws. I asked him about using it on a screw that goes into plastic, but he didn't really comment. He charged me $5 for labor.
She don't lie, she don't lie, she don't lie-- Propane.