How did all those errors creep in?
In preparing the new arrangement of Counting Sheep, I added some detail (and altered some of the time signatures), and so I have had it in mind that, the new arrangement done, I wished to create a fresh original-scoring Sibelius file.
Although one might argue that I am merely making more work for myself . . . it turns out that this supposedly-additional task is proving greatly added value, as I find several errors in my adaptation.
Probably, I am enjoying this entire process more than some right-thinking people could quite endorse . . . .