Score layout issue in C6 - unwanted page breaks

Hello -

I’m having trouble controlling the number of bars on a page.

My chart is 5-part acapella. I have 3 bars per line. On most pages, I have 5 staves on the top of the page and 5 staves on the bottom, as you would expect. But some pages only have 5 staves on the top and the bottom is blank. I can’t find any way to control this. Does anyone have a clue how to fix this? It’s like I have some unseen command inserted periodically.

Any help will be appreciated.