Yes, shackles may indeed be oblong after all this time. But, believe it or not, all the other bolts seem tight and void of play when I bounced the trailer up and down after launching the other day. Only the one bolt I initially mentioned seemed to have a broken bushing, like it wasn't even there.
Thanks for the suggestion abou wet bolts, too. I'm going to talk to the shop about them. I'm thinking wet bolts with nylon bushings instead of bronze. This way, if I later have greasing issues, or get lazy, I won't be metal on metal.