I have a five string fretless bass that's consistently had some issues with buzz on the lower strings. The D and G are fine, the A is good most of the time, but the E and B will buzz with any more than a medium-light touch. The buzzing is mostly in the lower end of the neck, say the first six or seven frets. I've loosened the neck about a 1/4 turn, but I hesitate to do any more because the mwah on the top strings is perfect as it is and I don't want to lose that. Could a new nut (or even some sort of filler like a couple strips of paper) be what's needed?