Hi everyone. I'm trying to fix up a beat up 6 st fretless. I'm very close to having it ready to play, except for one big issue that I'm not sure how to fix. At about the 12th (fret?) to the 15th there is a gradual depression in the fingerboard. It's deep enough that it causes the strings to mute any notes against the wood, making that portion of the neck unplayable. I'm looking for a DIY fix, as I'm trying to keep this cheap. I was thinking perhaps that applying epoxy, with a few extra thick layers to the problem area could do it. However I'm wondering if there's a better approach.