We’ve seen this before. If memory serves me right the last time was late last year. The market has continued to fall since. General consensus is that, whatever the cause of the stats, it is an anomily rather than any reflection on what is happening in the market.
My best guess is that this is down to banks restructuring the finances of one or more large developer. As part of the deal some or all of the developers assets are transferred to the bank. This in turn causes the blip in the stats.