Another fork between AntPoolofficial (losing) and FoundryServices (winning). While AntPool and friends started off mining an empty block on AntPool's block, they switched to Foundry's block with the next (non-empty) mining job

This looks to me like AntPool is pushing out empty mining jobs based on their blocks as fast as they can and only then send jobs created from a getblocktemplate call 30s later.

Meanwhile, their nodes had probably switched to Foundry's block as it arrived slightly earlier