I got a similar issue (I suspect the same root cause) when trying to set a default value for an Instanced property in the C++ constructor using CreateDefaultSubobject. When I changed the value of the property in a blueprint class, it wouldn’t be properly saved. Or rather, the property does get saved, but it is not loaded properly, or it is replaced by the default object after loading (I realised this when I commented out the CreateDefaultSubobject line after saving a blueprint with a modified property value and then it was loaded correctly).