Save dialog box opens in a collapsed view; won't preserve resizing

Whenever I go to Save a file, the resulting dialog box used to open with the list of files and folders visible, like so:

But lately, the dialog box opens with the folders panel collapsed:

I have to resize the box to see the files/folders. This used to preserve the new dimensions, but now it reverts to the collapsed view every time. That's got to be a bug, right?