Copy Paste - buggy behaviour

If you switch off View > Signposts > Hide Signposts, you’ll see that there’s a -1 Staves signpost at the start of the voice staff. (This is why if you switch to galley view, the voice staff doesn’t appear at all.) Delete that signpost, and all will be well.

Thank you. That does seem to solve the problem.
I’m thinking how that got there. I think I was trying to delete the stave up to where the singing starts, which I thought could be done.
Must of forgotten I did that.
In any case, is it possible to “erase” part of the stave? I thought you could.