Footnotes formatted with different classes

Hi friends,

I have been looking in the board for some question like this one, but found nothing close. I hope you can help me.

I am in the process of compiling an ebook, both epub and mobi. My problem is that the footnotes have different format one to the next one, affecting paragraph spacing.

I am using plain text in my preferences, and I have formatted all documents to Normal, but the footnotes are still in different formats.

I have opened the epub file with an editor and found that some notes have their paragraphs

(the ones I like, by the way) and others are

.

I have not found any way to format the footnotes.

Any ideas?

Thank you very much for your support!