[Plugin: Genesis Responsive Slider] More tag converting to span id!

I’m putting them in in the Text Editor of a WordPress page like this:

<!--more-->

and they’re coming out like this:

<p><span id="more-9"></span></p>

They’re are correct in the MySQL database but if you look in the HTML of the browser (View Source) they are the span id and therefore don’t do the job they’re supposed to.
I’ve entered the more tag using both the Visual and Text Editor but I can’t get them to work.

I use more tags on another WordPress install with Genesis Responsive Slider and they work fine. However on my localhost this is happening.

I’ve just tested more tags out on posts and pages and they work on archive pages. Therefore, this is probably a Genesis Responsive Slider issue – as it’s working on everything else, just not in the slider!

How can I stop this happening?

(I’m using Chrome on a Mac developing using localhost.)