Ann: Maiden Underground Resource , page-6

Maybe this may explain the drop in sp, a snippet from the announcement in this thread(page 6) -

The SAG mill liner issues have continued to impact production with monthly unplanned liner replacement during
the first four months of FY2010/11. The SAG mill issue is driven by accelerated wear of the liner and lifters
necessitating replacement on a monthly basis. Mechanically, the SAG mill is performing reliably and in line with BFS assumptions. Monthly liner replacement losses have been reducing continually since commissioning and the newly designed liner package which was installed last week is expected to significantly extend the time between liner changes. The ball mill, which receives the SAG mill output, demonstrates liner wear rates supporting the 2008 BFS assumptions, with the first liner change scheduled in December 2010.

The impact on production from the accelerated SAG mill liner wear since July 2010 are estimated at circa 4,500
ounces whilst the ounces lost from the delayed access to the ore body is estimated at circa 2,000 ounces for the
same period.