Dispatch queue 'mqtt client' was not executing error from camel-mqtt producer

Hi,

I'm trying to use camel-mqtt producer on camel 2.12.2 but it fails
with the error:

Caused by: java.lang.AssertionError: Dispatch queue 'mqtt client' was
not executing, (currently executing: 'mqtt client')
at org.fusesource.hawtdispatch.internal.SerialDispatchQueue.assertExecuting(SerialDispatchQueue.java:145)
at org.fusesource.mqtt.client.CallbackConnection.publish(CallbackConnection.java:585)
at org.fusesource.mqtt.client.CallbackConnection.publish(CallbackConnection.java:581)
at org.apache.camel.component.mqtt.MQTTEndpoint.publish(MQTTEndpoint.java:160)
at org.apache.camel.component.mqtt.MQTTProducer.process(MQTTProducer.java:58)
...(snip)...

I found MQTTProducerTest in the camel-mqtt tests is excluded in its
pom.xml, so tried to run it but it fails with same error. Is
MQTTProducer not supported on camel 2.12.2?

Thanks,
Tomo