macOS sharing dialog picker unresponsive

When I select an item in the Finder and select “Share->Tailscale”, I get a dialog box with a list of my online nodes, but none of the controls work. The scrollbar won’t drag, arrow keys won’t scroll. Even the Cancel button doesn’t work (though you can press ESC to dismiss the dialog).
Anyone else seen this issue?
Is this a conflict with some other Finder extension/app?
It’s 100% reproducible.