you mean block #286209 on blockchain https://blockchain.info/nl/block-index/468084/000000000000000087e4e2f178c86c6802f0f22c83e00edc59eae7694fe92b59

last month i`ve seen the same problem with another pool where i have some miners, the pool operator said that blockchain isn`t always right
https://bitcointalk.org/index.php?topic=27062.msg4644357#msg4644357