Blank lines in epub but not mobi

When I compile my epub, about 20 blank lines are randomly inserted throughout the manuscript. These do not appear in the mobi version.

I took the mobi version to Calibre to convert it to epub, and the blank lines were there after conversion.

What code mighit be causing this in epub but not mobi?

Thank you for your help. I’ve run out of ideas.

Just to clarify, are you talking about twenty blank lines altogether, or are they scattered throughout and being accounted for in an accumulated fashion?