Join syntax showing unusual results

Following on from a question I asked yesterday - (https://www.experts-exchange.com/questions/23499412/Add-an-additional-Join-to-an-existing-query.html) I now have a successful query as follows;


SELECT m.ID, m.shortname, m.retailer_name, o.merchantid, o.id AS oid, o.offertitle, o.offerbody, o.a_status, o.offerauthor, o.offershortname, o.clickcount, u.id, u.username
      FROM merchants m
    LEFT JOIN hurry_offers o
      ON m.id=o.merchantid
    LEFT JOIN hurry_users u
      ON o.offerauthor=u.ID
      ORDER BY oid DESC


I would now like to add a further join in order to get the number of comments against each 'offer'.  The query I currently have is;

SELECT m.ID, m.shortname, m.retailer_name, o.merchantid, o.id AS oid, o.offertitle, o.offerbody, o.a_status, o.offerauthor, o.offershortname, o.clickcount, u.id, u.username, count(c.offer_id) AS c_cnt, c.offer_id
      FROM merchants m
    LEFT JOIN hurry_offers o
      ON m.id=o.merchantid
    LEFT JOIN hurry_users u
      ON o.offerauthor=u.ID
    LEFT JOIN hurry_comments c
      ON o.id=c.offer_id
    GROUP BY c.offer_id
      ORDER BY o.id DESC

This works in as much as it is returning the correct figures for each element (i.e the correct username, comment count etc) however I'm only getting 2 results returned at the moment.  Unusually, there doesn't seem to be any reason that I can see for the 2nd of those results being returned - for example, it's not the 2nd row, it doesn't have any comments etc.

Having been working on this for some time, I'm hoping it's just something simple I've missed!

Any help would be much appreciated