Normally, property trees are serialized to clients via SDS, and external values (large blob values commited to disk) are lazy fetched on demand.
However, in some cases a ptree is serialized outside of the context of SDS, e.g. getFileTree which is called when a foreign file is read.
In that situation, the regular ptree serialize method is used, and the tree is deserialized as a plain ptree at the client.
There is a bug where external values are skipped during this process, and the client receives an empty stub instead.
This was noticed (reported as bug), when a DFS file lookup to a foreign Dali was being made, that had large ECL and _rtlType values, that had both been externalized. Neither were serialized correctly, and it caused the client fail to deserialize the type info correctly.