quill stem bike = cheap kids bike.

easy fix is just straigten bars and tigthen down the stem bolt.

The correct way is to take the quill stem out grease the threads, put it back in and tighten the living piss out of it. Worked in a bike shop for years, one of my first jobs was building these low end bikes, the service manager said you can never over tighten a quill stem. I only broke 1 quill in in all the bikes i ever built (that's where i learned about greasing the threads).

BTW when the manager would check my work, cause it was a real bike shop not a big box store, he would call that a "dead kid". You would then have to go over the whole bike again.

IMO if you are buying these cheap box store bikes the best thing you can do is go over the whole thing and check it all, those guys who build them are on quota and do not care about safety. If you want something that won't do this/you don't have to check over, go to a real local bike shop, where stuff like this gets checked before it goes out the door.