BP nativization can generate an invalid path including "__TEMP_BP__"

The licensee sent us a BP that can't be nativized correctly on UDN.
The nativized BP has wrong paths and causes a crash.

1. Open the attached project
2. Open Content\Blueprint\System\Stage\BP_StageManager.uasset
3. Generate C++ code by File/Developer/Generate Native Code
4. You can see in the generated code that some paths include " _TEMP_BP_". And the paths don't exist.