My Ken Smith BSR5GN played like a dream when I bought it last year. Action was right with no buzz on the frets. I left it in a mono bag standing upright for the past 2 or 3 months without much action since acquiring other basses. Yesterday when I took it out for a spin, I noticed a bad fret buzz on the E string at the 6th fret. There is a slight buzz on the B string at the same place but it is not as pronounced. What possibly be wrong here?