Priority support for non persistent messages is broken if all messages remain in memory. The first dispatch will in receipt order so the consumers ordering is not sufficient.
Problem: the default store cursor uses a file pending cursor for non persistent messages, but the in memory list is not priority aware.
Work around: is to use the vmCursor or to disable broker persistence.
Fix: is to make use of the PendingList from a vm cursor for the memory list of a file pending message cursor.