in player.xql I've added "/text()" to the end of these three lines to force the query to return a string rather than an element.
{$movie//tei:person/tei:trait[@type='description']/tei:p/text()}
let $title := $movie//tei:titleStmt/tei:title/text() | $movie//tei:titleStmt/tei:title/tei:title/text()
let $relatedTitle := $related//tei:titleStmt/tei:title/text() | $related//tei:titleStmt/tei:title/tei:title/text()

If I return a string:
- I do not get the text of any embedded elements (e.g. the title of a publication in the title of the interview), which is why in the $title line, there is the or condition which at least returns the text of the embedded title, but not as a title for styling
- the output validates
If I return the element:
- I get a validation error "element from an unrecognized namespace" in the output xhtml
- I'm not sure what happens with embedded elements, presumably more validation errors.