Xcode 16's "Stage All" button does nothing most of the time

1. Use a project hosted by a filesystem/local Git repository.
2. Make changes to any file in the project.
3. Switch to the "Source Control" Navigator, and the "Changes" sub-navigator within that.
4. Select "Uncommitted Changes", or any file below that.
5. Verify that your changes appear in the source change browser/editor on the right.
6. Click the "Stage All" button.

Absolutely nothing happens, 90% of the time.

1. Go back to the Changes navigator, right-click on an item there and select the "Stage Changes in..." popup menu item. It works, every time.

I haven't found any pattern to the 10% of the time the "Stage All" button actually works, wrt what changes are selected in the navigator, whether I've already typed a commit message, etc..

I happen to be using Xcode 16.0 on two Macs: a Mac Studio running MacOS 14.6.1, and a 2019 MacBook Pro running MacOS 14.7.1. Both exhibit the same symptoms.