Just a thought, but given the time of year I wonder if there is a forced seller- stock held in company name with y/e 31/12, or an overseas holder with a tax y/e 31/12- not saying this is the case, just speculating. Also, sometimes MM like to clear their books by y/e if that's the way their company reports. Just idle speculation, but I've got little else to offer at the moment.
Edit well thin markets move, particularly at this time of year when MM desks are being run on a 'no new position basis', until the more experienced MM's return from hols.