I have an Ovation Pacemaker 12 I bought back in 1980 that I dearly love. It appears to have a neck issue but nothing that is obvious to the eye.

I can tune the guitar and it will hold that tune well. However, if I capo it, say on the 3rd fret, 2 of the strings (B & G) go out of tune sharp while the others stay in tune to each other.

Is this just a neck straightening issue or is it something else?

Also, what's an average cost for straightening an acoustic neck?

Thanks,
Dave