After not playing much for 15 months we've got a gig so I dragged out my gear, tuned up and set the intonation perfectly at the 12th fret. I found that I was out of tune - check tuning on open string, perfect - 12th fret, perfect. But at the 5th fret and below I was out by an eighth to a quarter of a step. What's going on here? I've had this Sadowski for 4 years and never had an issue. Any ideas on how to fix this?