I have recently discovered that if you were to create two objects of the same type which have a priority array (e.g. BV), if you set the Priority at index 3 in BV1, it will also set it in BV2. This happens because in ObjectProperties.java, the static add() function creates a new PriorityArray instance which is then passed into all objects of the same type when they are created. This means the same PriorityArray object is used and passed into all BV instances when they are created.
The solution to this is to after creating your BACnet object (AO, AV, BO, BV etc), call the setProperty() function, and create a new PriorityArray instance;
BACnetObject bv1 = new BACnetObject(.....);
bv1.setProperty(PropertyIdentifier.priorityArray, new PriorityArray());