Try This
Had a similar problem on my son's Cort guitar. Found out the the nut was cut too deep, on the G string only.I packed the G string nut slot and it cured it.
I used a sliver of a top E string and laid it in the nut slot and carefully lowered the G s, brought it to pitch. Sorted.
Had a similar problem on my son's Cort guitar. Found out the the nut was cut too deep, on the G string only.I packed the G string nut slot and it cured it.
I used a sliver of a top E string and laid it in the nut slot and carefully lowered the G s, brought it to pitch. Sorted.