it was a standard 3/8 bolt using, standard practices. no loctite, over-torqueing, etc.
what ive noticed with many bolts placed at index, during the first couple years it seems that freeze thaw can loosen the bolts a bit, requiring re-tightening, which usually takes care of the problem. (or maybe its just the train vibration/5th force combo thats the culprit.)
im going out today, ill have a look.