Interesting is the assumption the call maker made a mistake of some kind. From a call makers standpoint, every attempt must be made to ensure a call doesn't fail in the field. Most of us are not making calls to earn a living, we do it because we love it and want you, the hunter, to be successful in the field. Countless, and I mean countless hours are spent in the shop perfecting our skills. I and many other call makers can attest to the personal sacrifices made to learn this craft, which for many of us is more like an obsession. Our reputation rides on every call that leaves the shop.
One of the things you learn as a call maker, is that a call has to be foolproof. Hunters will sometimes think they can adjust a call to make it sound better. Maybe they can, if they know how to tune a call. For example, a predator or duck call made with a Lousiana tone board. A hunter takes it apart thinking he can adjust it, tune it or whatever, puts it back together and it sounds even worse. Because he doesn't know where the reed should be placed on the sound board for optimum sound, he is now even more frustrated and blames the call maker.
A screw on a box call might be glued in once the call is finished and tuned to prevent the hunter from making adjustments, not to make it difficult for the hunter, but to keep the lid in the optimum position for making turkey sounds. It might also be done if the call is being sent in to a competition for the same reason. These calls get handled a lot, and things can happen to screws. If it backs out a half turn it can dramatically change the sound of a call.
If you are having a problem with a call, do yourself and the call maker a favor by contacting him/her first. Sometimes a situation can be prevented by a simple phone call and a drop of release agent!