The following event sequence will lead to double deallocation of a producer batch.
1) a producer batch is sent and the response is not received.
2) the inflight producer batch is expired when deliveryTimeoutMs has reached. The sender fail the producer batch via "failBatch" and the producer batch is deallocated via "accumulator.deallocate(batch)".
3) the response for the batch finally arrived after batch expiration, and the response contains the error "Errors.MESSAGE_TOO_LARGE" .
4) the producer batch is split and the original batch is deallocated a second time. As a result, the "IllegalStateException" will be raised.