Hi,
The help file under Part Markers explains this better than I could:

"When you’re reading a book, a new section begins on a new line, with space between. Band-in-a-Box does that for chords too. Whenever a new section occurs (a part marker), we start the new section on a new line and draw a grey line above to clearly mark the new section. You’ll see each section on a new line so that the form of the song is easier to see.

For example, if you have a song with a 7-bar section, followed by 8-bar sections, earlier versions of Band-in-a-Box wouldn’t start the other sections on a new line. The result was that it was hard to delineate the sections, as if an entire story was told within one paragraph."

You can prevent this behavior by clicking Options then Preferences then Display. Remove the tick from the box labelled "New Line For Every Section"

Regards,

Richard Williams
Sydney
Australia