InDesign is selecting the wrong page in page display
I wonder how much time this bug has wasted.
I noticed that when changing section-specific info in the Layout / Number & Section Options menu, sometimes it would produce totally unexpected results and screw up multiple sections and page layout.
It turns out that this is because pages are inexplicably selected in the Pages tab, unrelated to where the insertion point resides. Sometimes two pages are selected at once in that pane, other times only one... but frequently the selected one(s) is wrong. I didn't select it, and it doesn't reflect the page on which I'm working.
Further experimentation shows that it usually selects both pages of a spread, instead of the one you put the insertion point on. That is a major PITA; if you click on the right page thinking you're going to start a new section, InDesign will instead start the section with the left page, messing things up.
With the insertion point sitting in text, I expect any changes made to the section or chapter options to affect the section in which I'm working; not in some arbitrarily (and automatically) highlighted thumbnail in a disconnected pane.

