Hi,

The dataypedictionary system is complex. Initializing our implementation/support for it involves a lot of Read and Browse calls in multiple steps and currently unfortunately does not have very good error reporting if something does not work.

What server is this? What version of OPC UA it supports? (i.e. if it is a 1.04 server it could have something we do not yet support).

This is a bit complex, but is there any node that cannot complete all 3 steps?:
1. Taking all HasComponent target nodes from all nodes under Root/Types/DataTypes/OPC Binary
1.1. e.g. example Root/Types/DataTypes/OPC Binary/Opc.Ua/AddNodesItem
2. Taking all nodes as result of 1, do they all have Inverse HasDescription reference target?
2.1. The AddNodesItem in 1.1. would point (the source of the inverse reference): DataTypes/Structure/AddNodesItem/Default Binary (note that this is non-hierarchical reference and might not be seen in normal clients UIs)
3. Taking all nodes as result of 2, do they all have Inverse HasEncoding reference that is a Structure DataType node
3.1. The Default Binary node of 2.1. would point (the source of the inverse referene): DataTypes/Structure/AddNodesItem

Based on the code a NPE would be possible if a node would fail to have the inverse reference in steps 2 or 3., error reporting could be improved in a future SDK version.

P.S.
Also it should be noted that technically the datatypedictionary system is a complete parallel system in the specification vs. the normal encoding system. Our implementation takes a best-effort attempt for linking it with the normal system, i.e. uses the data from it and constructs encoders and decoders. Normal system works on NodeIds that works on the Namespace + id value, the datatypedictionary system works on XML Namespaces and Names (the dictionaries are encoded XML documents) and a normal Namespace can have multiple dictionaries with different XML Namespaces. It is possible that the UaExpert implementation is different. Also it is possible that this is a UA 1.04 server and UaExpert would support the complete new system of 1.04 i.e. the new DataTypeDefinition Attribute.