I Had This Problem on a Strat Neck...
....what happened over time, is that the wood on the fretboard, where there was a small knot in the wood, became a little raised, relative to the rest of the fretboard
and raised one fret slightly. That fret would be dead right where that detail in the wood was. My luthier made two-three passes with the fret crowning file, and brought that fret down to the same height as the others. I don't even think he charged me. Now, it's fine. But, I had a devil of a time figuring out what was causing it, and I couldn't correct with any set-uup changes, either. It was dead no matter what I did. But, the fix was easy. Could probably do it myself with a steel rule and the right fret crowning file.
"I don't know if it's art, but I like it."