Pages with one or two measures

I'm new to MuseScore. The new orchestral sounds have called me. They are VERY good. However, my first project imported from Sibelius via MXML insists on putting only one measure on some pages (sometimes two). The measures don't have any more notes per measure when this happens. I've tried using the Stretch option, it doesn't do anything. I've removed all system breaks (although I doubt there ever were any). I don't want to change the spacing options as most of the pages look fine. I know this question has been asked before, but after perusing the answers I'm not getting it fixed.

Thanks