The library QueueArray.h doesn't handle properly the status of "Empty Queue".
When the queue is empty if you try to "queue.dequeque()" or "queue.front()" the system fails ... I can't tell how, but the Arduino controller behavior becomes unpredictable and unstable.
Yes ... it's easy to implement an IF check " ... if ( queue.count() > 0 ) { ... " but is not documented and for a beginner takes time to understand ... debug ... and workaround the issue.
Thanks for your attention
Regards
Andrea