I recently got an acoustic guitar for much cheaper than it’s worth because it got a crack during shipping and they had to sell it cheap. I’m overall happy with it except that it has a rattle when I play the 5th and 6th fret. I believe it’s because of the crack but I’m not 100%. The place I got it from did some work on it to fix the crack but I want it done professionally. Any idea on what else could cause the rattle/how to fix the crack?