It's seems odd that the bolts should bottom out (if they are original) however the quick fix would be to put a washer under the bolt head to stop them bottoming, you could use spring washers ( a bit thicker, plus added security) or if flat washers are enough Loctite the bolts but give them a good degreasing before applying the Loctite.
I lost a bolt on the way from Italy to Spain and a Guy in Arles found one to fit and used some loctite hasn't budged since.
