Yup, disabling the sort and pagination settings did the trick, so the issue is there.

I suggest refactoring the theme code so that when outputting html via concatenation of strings, to use single quotes on the php strings and double quotes for the outputted html tag attributes. i.e.:

$output .= '<a href="#" target="_blank">' . $some-user-var . '</a>';

(hopefully the code tags here will work and not mess up my example…)

Over my many years in php, I have found this to be the best approach, if you go over your code and do this you will likely solve many irritating and difficult to find issues such as this.