I've been doing some additional research, and came across an additional solution that doesn't involve macros:

1. Select the first instance of the black block.
2. Press Ctrl+Shift+P. An "Apply Style" dialog displays, showing the selected paragraph style.
3. Select Reapply. The problem should be fixed.
4. The source for this suggested immediately right-clicking the style in either the Quick Styles bar or the Styles Pane and selecting Update to Match Selection. I did not have to do this step; your mileage may vary.