System length

I downloaded a piano version of Johnny Mandel's Emily from the MuseScore library and am making a sketch score for horns and rhythm section with chord symbols. The last 4 bars of the last system in the trumpet and piano parts won't spread across the page. There are four bars, but they are short bars, compared to the rest of the part.
I can't figure out how to get that last system in the Piano and Trumpet part to be the same as the other systems in the part.

Jeff
Springfield MO