A tool free adjustable stem? I hope that the company has good lawyers Hinged stems almost always develop a bit of slop as they age. Keeping the joint and any wedge tight will help limit this. of course since your stem is tool free I don't see why you are having the problem in tightening it. Just do it.

That last bit is satire. Really if you want more specific help you need to provide us with more info, photos, what you've tried to do already. Andy.