What exactly do you mean by loose? Is just the top part wiggling in line with what Spazz described? Or do you just mean that the top part is inching back and you have to turn the knob every now and then to raise it forward again? I'd be pretty concerned about the former (don't think that is common or normal), but not so much the latter (which I suspect is fairly common and has been discussed here before). In the case of the former, I'm guessing you'll have to do what Spazz did, but in the case of the latter, I don't know of anyone having a solution for that yet.