When using the new 7.1 lucene feature of querying attachments there may be duplicates in the result if:
- Setting "doctype" for the query to "all"
- The query matches both, a document and a file attachment of the same document
- The query is either processed in an indirect manner, like reading results to a list and then putting them out, or on the last page of a <tml:foreach> with "filllastpage" being true (which is the default)