I just put my conspiracy hat on.......

How about it is a simple case of just one party with multiple accounts selling to itself (hence no share is lost), with the explicit purpose of driving down the SP.  Hence it would achieve the purpose of lowering ARU's share price and pick up the shares from the panic sellers, as well as geneating a wave of margin calls that put even more shares out in the open market cheap.

It's just a theory.