After the Polkadot 1.7.1 runtime upgrade was enacted, only the AssetHub runtime was upgraded, not the BridgeHub runtime. This caused a mismatch between AssetHub and BridgeHub runtimes, while in turn caused Snowbridge transactions from Ethereum to Polkadot to fail.

Full incident report: https://forum.polkadot.network/t/snowbridge-incident-report-polkadot-runtime-upgrade-1-7-1/15144

6 transactions from Hydration to Ethereum failed. This referendum replays those 6 transactions, to complete the transactions.