"Transaction has not been started" errors and stuck messages with ActiveMQ RAR on EAP and XA transactions

An application based on MDBs running on JBoss EAP consumes messages from an A-MQ broker, reads (but doesn't write) an Oracle database table, then posts messages to one or more other destinations. All destinations are on the same broker, and all these operations take place in the scope of an XA transaction. The application has about thirty different MDBs, and uses only container-managed transactions.

Under heavy load, there are occasional "transaction has not been started" exceptions between the transaction prepare and transaction commit/rollback phases. These exceptions seem to be related to messages stuck on the broker, that cannot be consumed without a broker restart.