We'll need the exact HTML snippet of such a scene break/PoV shift (which you can access in one of the highlighting menus, IIRC, although since you have Calibre open, that works, too
), as well as any Style tweaks you may have enabled (that's in the top menu > Document tab > Style tweaks), and whether you're actually set to honor embedded styles at all (that's in the bottom menu > Gear tab, IIRC).