#1
I have a somewhat old acoustic that has an issue with the 13th fret on the high e. Fretting the 13th fret results in the same sound as fretting the 14th unless I give it a slight bend. Aside from a few dings, it's seemingly in good condition. Any advice on a possible cause and fix would be helpful. Thanks.
#2
Either the 13th is too low or (more likely) the 14th is too high. Any decent guitar tech should be able to quickly put a gauge on these and determine which is the culprit, and then "dress" (file down) the offending fret.
Sometimes, the frets actually start to work their way out of the wood; in which case they can usually be repaired by either forcing it back down along with some glue or replacing altogether with a slightly-larger piece of fret-wire stock.