if i'm right the solution is quite simple. there is a song option default that says 'vary style in middle choruses' and other settings you might like to play around with including pushes etc

take a look at song settings. i think that that default means chorus 2 is played with the b style which is diffent to the a style used in chorus 1 and 3. if that's what you like set all the part markers to green and the b style will play all the way through