Structure default values appear to still not be working properly unfortunately.
UE-12206 GitHub 944 : UE-12128: Properly save structs when struct field default value is different
https://answers.unrealengine.com/questions/190159/undefined.html
I think it works if you have no inheritance (one BP class with no children). But if you have inherited BPs using these struct and you set the values to new values, then the bug comes back (click compile and some values are zeroed).