step bar loose

My "new" 2011 1500 sport has what appear to be factory step bars on the sides to aid in stepping up to get in. when i was test driving and such, i was mainly getting in/out on the drivers side. while i opened the pass side up to check things out, i never actually stepped in. so, the first week i owned it, whenever my girlfriend got in or out and stepped on the bar, i could hear a click sound. i checked it out and that side was a bit loose, especially with my heavier 190# butt stepping on it. crawled under and tried to tighten the bolts. none were appreciably loose but i got a turn on all of them. i didnt know what exactly they screwed into so i didnt over do it for fear of stripping them out. the drivers side is tightened to about the same level (i can go more but the dr side is fine as is). anyways, after tightening, the click is gone when stepping but there is still more flex on that side compared to the dr side. anything else i can do? there any limitations on weight for these things?