Partitions that are in the WorkingSet and are later dropped will remain in the WorkingSet forever. To reproduce, added two partitions to a PartitionedFileSet and set the ConcurrentPartitionConsumer's ConsumerConfiguration with a maxWorkingSetSize of 1 and the timeout of 60. Execute consumePartitions and mark the partition as failed with onFinish. Drop the partition that was marked as failed. Call consumePartitions again and nothing will return because the failed partition that was dropped is still in the workingSet.