staff extending after piece is over

[Kieren MacMillan]

Hello, all --

My score [v2.8.4] gives this at the end:

I use bar checks at the end of every single measure of every part,  
and my score compiles with no errors.
Any idea what's going on, or at least what I can do to get Lilypond  
to tell me why it's extending one of the staves?

Thanks,
Kieren.