Compile changes the formatting

I’ve created two paragraph styles. Both have line spacing of 1.1. One paragraph style has big spaces between lines after compile, as if “doublespaced,” not at all resembling how it looks in the editor. How can I fix this?

A page break has appeared between scenes, after compiling, where there shouldn’t be one. That location has no chapter break or other type of break. A block of one paragraph style ends and the other of my two paragraph styles begins, as happens often throughout, but at this location Compile puts in a page break. How can I fix this?

I have experimented with Compile > Assign Section Layouts, carefully changing only one thing at a time and seeing what happens. I’m stumped. Thanks for any help. I have found it impossible so far to have a good understanding of how those Assign Section Layouts choices work.