There is still some (but very little ... when reproducing this you need more than 100 runs in half the cases statistically) instability left in the test
Resulting in this exception being thrown at a relatively low rate (I'd say def less than 0.5% of all runs on my machine).
kafka.api.ConsumerBounceTest > testConsumptionWithBrokerFailures FAILED
java.lang.IllegalArgumentException: You can only check the position for partitions assigned to this consumer.
this was also reported in a comment to the original