Bar cannot be shrunk from stretching across whole page (file attached)

Hi there,

In the attached file, I would like bars 16-31 to fit across two lines/rows (apologies if these aren't the right terms; my theory knowledge doesn't extend far). At the moment, they occupy three, largely because bar 16 stubbornly refuses to shrink down from occupying the width of the page.

If you can help me achieve this and, even better, explain how I can avoid this in the future, I'd be much obliged.

Steve :)