Problems with random leading (line spacing)

Scattered throughout my project are places where the leading goes wonky. Judging by the info in the ruler and a look at the formatting revealed by hitting the “Invisibles” button it seems as if the line spacing is as it should be (2.0) but in these particular spots it’s clearly not—there looks to be an extra line space between the lines.

Any ideas about what might have happened/how to fix? Highlighting the problem areas and clicking on the ruler spacing button does nothing to fix it and in the main preferences panel the spacing is set to 2.

Thanks very much.

Deb