Not sure why it happened, but we had major problems when Chapter 16 was uploaded. The timeline is as follows. First, I uploaded Chapter 16 and it worked fine. I read the story, and everything was in order. Five minutes later, I added Section headings, which is how I originally wrote the story. I then checked the Table of Contents and it all looked fine. However, it seems that adding the sections screwed everything up. Everybody focused on the problems with Chapters 15 & 16, but it was throughout the story. Chapter 2 was missing, other chapters were wrong - basically the whole thing was a mess!
I dumped it on Lazeez, the webmaster, and got the following response: “I checked the story. I found no duplicates on my end. I cleared the story's cache on the server. Please check and let me know if that fixed the issue.” That seemed to do the trick. Please check.
Fixing this was both heartwarming and a major nuisance. I had forty-plus responses, which is very heartening. However, I also try to respond to everybody, which meant I had to respond to forty-plus mentions of the problem! Thank you all!