I am having a similar problem with a Mike Lull 54P I just bought used. G string at the 8th fret is dead, no sustain. All of the other notes ring out clear. Adding my tuner to the headstock improves it slightly. I have never encountered this phenomena in such a pronounced way, I'm a little bit frustrated about it and I'm experiencing some buyers remorse. I'm going to try a few adjustments since I didn't notice any dead spots during my test drive.