Have ended up commenting out a line of code under pinboard_move_elements() within functions.php.
var video = $(‘.entry-attachment’, container);
if(‘undefined’ !== typeof video)
//$(‘.entry-container’, container).before(video);
I don’t know what it doesn’t like specifically about Portrait mode on iPhone in Safari but the fix will have to do for now.
Happy to hear from anyone else that may have had this same problem or if there’s a solution that doesn’t require changing the code.
Cheers.