The new high availability feature of KIP-441 relies on deterministic assignment to produce an eventually-stable assignment. The HighAvailabilityTaskAssignor assigns tasks based on the unique processId assigned to each client, so if the same set of Kafka Streams applications participate in a rebalance it should generate the same task assignment every time.
Unfortunately the processIds aren't stable across restarts. We generate a random UUID in the KafkaStreams constructor, so each time the process starts up it would be assigned a completely different processId. Unless this new processId happens to be in exactly the same order as the previous one, a single bounce or crash/restart can result in a large scale shuffling of tasks based on a completely different eventual assignment.
Ultimately we should fix this via KAFKA-10121, but that's a nontrivial undertaking and this bug merits some immediate relief if we don't intend to tackle the larger problem in the upcoming releases