My last bike was a 19.5" 3700 trek 2008. I had it for 1.5 months before I realized I needed a bigger bike. They let me trade it in for a 21" 3700 trek 2009 and I paid the difference. I told them what was wrong and I came back an hour later to pick it up. I still noticed the problem, but it is only a slight weirdness.

They fixed the loose kickstand, put air in the tire, looked at the front brakes which were fine depending on how you put the front tire on, and put little caps that cover the hole in the petal. Maybe they didn't even ride it, I am 6'3"on a 21" frame, and the mechanics all looked well under 6'.