Ok, so they are held on with short unique bolts; they have short threads and long shoulders. You probably know this but just in case someone put something else in there. If you have the right bolts and they will not tighten, you will need to replace the lock latch as it is stripped out. they are made of pot metal and once stripped not much you can do. If you don't want to buy new latch/es, you can try a small piece of electrical tape on the threads to try and tighten them up. You best be is just to replace the latches.
