There is a regression between ER3 and ER4 builds. Proton clients cannot receive messages from the broker. This affects following supported clients: qpic-cpp legacy client, Proton c++ reactive client and Proton python reactive client.

On ER3 build the behaviour was not ideal as well. The client could send and receive a text message but the client gets stuck afterwards (after transfer is done). The message is removed from the queue on the broker.

On ER4 the the behaviour is similar but different. The client can send but can not receive the message. The client get stuck earlier (before the transfer is done). It seems that the message is acquired but not accepted so returned to the broker queue. In results there are most probably two duplicate messages on the broker queue.

This is most probably related to ENTMQ-1573.