What is a rollback_bet_settlement?

This is a dedicated feed message that tells you there was a change in the resulting of the market. The Rollback_bet_settlement messageinforms you for which markets the settlements have changed and that there will be a new settlement. The decision on how to react to this information is on you – you can either take back the payouts for the original settlement from the users and process the payments according to the new settlement, or you can leave the funds to the new players as some kind of a bonus and just pay out the "new winners", or you can just ignore it. Settlement rollbacks should happen only in rare cases, and you should also be notified about them via your preferred support channel.