According to CoinMeta, the Bitcoin Core and v29 nodes detected two valid candidate blocks at block height 963,853, both of which were mined by Spiderpool. Since their cumulative workloads were the same, there were temporarily two candidate versions in the network. Approximately 27 minutes later, F2Pool mined block 963,854 on one of these versions, which then became the main chain, while the other block 963,853 became an orphan block.