Sorry, it was just double quotes hack for line 79 in rc_foldersort.js.
$('#rcm' + orig_col).removeClass("'sorted' +
(orig_order.toUpperCase())");
Now for a temporary fix for "me" in rc_foldersort plugin; works immediately and no error in web console and RC after replacing line 79 with this 2 lines.
new_order = orig_order.toUpperCase();
$('#rcm' + orig_col).removeClass('sorted' + new_order);