With a huge amount of updates generated in a loop (such as upon a subscription for 130000 items all of which produce a snapshot) the mentioned _queue object can grow significantly, but we expect that all the contained strings are released before they are sent through the network.

Can you confirm that you could see strings hanging in the queue after the Adapter had terminated the transmission of all the updates?

Otherwise, it is possible that at very high update rates the library can never manage to empty the queue completely.
Would you notice the same issue by lowering the number of items, or would you notice a threshold effect?

About the continuous creation of large array objects, can you identify some of them?
The mentioned _queue object is never recreated, but its internal components may and this is an aspect that may leave room for optimizations.