[wpdm_tree] Not sorting correctly

I have [wpdm_tree] running, and show documents from a category. However I have told it to sort by ‘title’ and order ‘asc’ – this works for some of the files by others seems to appear in a random order below the ordered files.

http://www.kingsleyschoolbideford.co.uk/about-us/school-policies/

I’ve tried deleting and recreating the files that are ignoring the ordering but it still does the same.

Any ideas?