Squashed multibar rests

Hello Dorico users
I’ve got a flow with a “Voice” line above Choir Reduction. 3 staves. There is a four bar intro in multibar rest format.
The “Voice” line is a descant, so I want it hidden till near the end of the flow.
When all staves are showing, it’s fine. The four bar multibar rest takes up about 30% of the line, as you’d expect.
But when I hide the “Voice” line (Staff>Manual Staff visibility), the multibar rest crushes up to about 3mm wide.
Any idea why this is happening and how to fix it?
Many thanks.

I’m guessing you may have removed the bar rests. With no entries in a bar, Dorico has nothing to space.

Thanks. That sounds like it.
Problem solved eventually.