Holy Grail wizard got every exposure bump except for one. Why did it miss that? What can I do?

Also see this image.

I think HG Wizard is working correctly. But since your adjustments are very close to each other (no frame inbetween) it does not get totally smooth. But you can easily smoothen this with the visual deflicker. If one pass is not enough, use the refine option.

Next time take care to leave 2-3 frames inbetween before each adjustment to the camera.

Thank you!