#238 Undo/Redo and Progress Marker

[CCV]

Sometimes, using Undo or Redo causes Progress Marker to wrongly display 100%.
Not all that often really and, as far as I can tell, entirely at random.

What happens rather more frequently is that Progress Marker flickers briefly when Undo or Redo is used. Normally this happens too fast to tell for sure, but when it is slowed down by some other program(s) running I can see it does show 100% for just a fraction of a second.
Mostly when Hard (or Unfair) steps remaining; not so much on Medium or Easy steps.