Vexing problem with stave spacing during input

The piece is for violin and piano. When inputting notes and I get to the end of a system, the new system may end up on the next page even though I only have 1 system on the current page, and sometimes the individual staves of each system are far apart. I haven’t had this problem in the past, is there I setting I need to check?

Check Layout Options — vertical spacing — justification, fill frames?

If you can’t solve the problem by way of the settings on the Vertical Spacing page of Layout Options, I would recommend that you attach the project here so that we can take a look. Unfortunately it’s almost impossible to diagnose such problems in a practical fashion without seeing the project itself. (868 KB)
Here it is. I have been fiddling with the vertical spacing but this still happens:

P.S. and in this particular instance the brace now spans all 3 staves and the upper voice of the piano has bled into the violin part.