Arms Won't Stay On

I really wanted to like these sunglasses. The lenses were terrific. After maybe a month of normal use and gentle care, however, one of the arms began coming off at the hinge. After another month, the other arm began coming off at the hinge. Very disappointing. I've tried several times to make the hinges tighter to hold the arms on (there are no screws), to no avail. If anyone has ideas on how to tighten their hold on the arms -- without glueing the arms in place -- I'm open to ideas.