The body classname for slides are supposed to be fp-viewing-{section-anchor}-{slide-anchor} and this matches if slides are located starting from second section and so on.
However, if the slide is on the first section, the body class stays as fp-viewing-{section-anchor}.
Example:
https://codepen.io/meceware/pen/QwNxEVV
Reproduction steps:
- Check body class after loading the page (see
fp-viewing-0)
- Change slides and go back to the previous one and check the slides again. (see
fp-viewing-0-0)