Error expiring reference

The broker is throwing a couple of warnings when processing AMQP messages sent by a C client (Qpid Proton). This error occurs only when the broker is configured to work on a cluster. The problem seems to happen with any client, regardless of the language.

Steps to reproduce:
1. Configure a cluster of brokers
2. Send a message with TTL

Expected behavior: the message would be processed without errors

Actual behavior: the broker prints error stating that "Error expiring reference".

I attached two stack traces. One raised when the messages were sent via C (Proton) stack-trace-c.txt client and another raised when the messages were sent via Java JMS client stack-trace-java.txt.