Because FlexSlider (and other Views Slideshow integrations) only allows one field as a "Caption field", I regularly will add multiple fields to the view but hide them from display. Then I'll use a single "Global: Custom text" field to combine them all into a single field. The global text field usually has text like this:
This makes it so that I can have any combination of fields I like as a caption.
Unfortunately this doesn't work with Flexslider Views Slideshow, because it *forces* the custom text to have a wrapper of a P tag. This apparently breaks the custom text area.
I'm not sure why a P tag would be a reasonable choice to begin with. Even in flexslider-container.tpl.php, a Div is used. For both consistency and to restore the ability to use custom text fields in Views Slideshow, the aggressiveness of Flexslider's Views integration should be lessened.