Growth in Queue Memory Usage Statistics, Even Though Actual Memory Usage is not Increasing

We are observing slow growth in the reported usage for queues in two of our activemq instances, even when the queue size returns to 0. It appears that periodically, a message is dequeued without a corresponding decrease in reported memory usage. Looking at the heap, we can see that the reported usage is much higher than the actual usage of the Queue object.

We have tried upgrading to A-MQ 6.3.0 R6 and also avoiding purge operations in the instance, in case the issue is related to ENTMQ-2105, but we are still experiencing the issue.