A new problem.
I just uploaded the updated versions of the three books to KDP. Just to be clear, these do not have a correction for the start problem, because it is believed that KDP fixes it. So these are directly from Kindlegen.
I used the online previewer. Set to Kindle mode, all three books start correctly. Set to Fire, one starts correctly, one starts too early, in the TOC, and one starts too late, part way down the first page.
All three start correctly using the previewer on the PC.
I suppose what this means is that the online previewer has the same problem that the K3 has, but only shows it when set to Fire mode. This is all getting more and more complicated.
Question. How are we sure that uploading to KDP does fix the problem? I would have to buy one of these books to be really sure. And I would have to buy a Fire too, just in case they add a problem and the online previewer is right!