I can't duplicate a problem like that.
I made a test song, that just has 8 bar sections, of going from 1 to 4, in these keys C, A, G
The transitions all sound fine to me. Is this what you are hearing?

This uses 631 for the guitar: Real Tracks-PopAmericanDirty Ev

http://nn.pgmusic.com/pgfiles/jazzu/misc/631_1_to_4_test.wma


Have Fun!
Peter Gannon
PG Music Inc.