I use the trusty steel ruler to search for the problem...
My old Ibanez acoustic clearly has a concave fretboard. ?
The ruler touches the first fret and the last few, but the middle is bowed by half a mm...
This could indicate that the truss rod needs to be stiffened :-\ I don't think the bridge needs to be raised as there is already a two and a half mm gap between the unpressed string and the final frets.
The problem will manifest itself around the 3rd to 5th frets because I'm pressing the string, and it's touching higher up the fretboard. :-[
With a strat style electric guitar there are more ways to do minor adjustment at the bridge... set the height and length of the strings (get someone to show you how to set the intonation).
The indentations on worn frets should be clearly visible if they're the cause of the problem... ???
methinks... :-\