I just picked up a used Yamaha RBX 760 4 String bass guitar. I put new round wound strings on it and had the neck adjusted. The only problem is when I play the G string on the 12th fret, it sounds like it is muted, it does not ring like the other notes. I can play up and down the neck on that string and it is only muted on the 12th fret. If I press down lightly, I can get it to sound. But if I use regular finger pressure, it stays muted. Just wondering what the issue may be? Thanks.