According to Jihana Wu, co-founder of Bitmain, the reason for the empty blocks minning by Antpool's mining pool is errors in the operation of the equipment.
BCC/BTC mining together caused lots of error in the mining pools and empty block is a fall back security measure. It is solved now.
— Jihan Wu (@JihanWu) 25 августа 2017 г.
Shortly after the activation of the Segregated Witness protocol, the world's largest mining pool produced six blocks of less than 1 KB in size. It is worth noting that the empty blocks were also extracted by the famous Chinese pool BTCC.
During the production of empty blocks, there has been an increase in the number of unconfirmed transactions in the bitcoin network. So, on August 25, the number of unconfirmed transactions was about 90 000, and their size exceeded 100 MB.
Currently, the number of unconfirmed transactions has declined and is less than 35,000, the size of the mempool is slightly less than 70 MB. This reported by the blockchain.info.