Adding a variable to a Structure after packaging then repackaging causes the package to fail

This is not a regression. Tested in //UE4/Release-4.27 CL18319896

Adding a variable to a Structure after packaging then repackaging causes the package to fail.

1. Create or open any project
2. Create and save a new Structure named 'ST_Test'
3. Create a new Blueprint Actor
   1. Add a new variable of type 'ST_Test'
   2. Compile, save, and close the Blueprint Actor
4. Package the project for Windows
5. After successfully packaging add a new variable to 'ST_Test'
6. Without making any changes to the Blueprint Actor package the project for Windows 

Expected Results:
The project packages successfully.

Actual Results:
Packaging fails with:

PackagingResults: Error: FStructProperty::Serialize Loading: Property 'StructProperty /Game/BP_Tester.BP_Tester_C:Struct'. Unknown structure.

OR

1. Create and save a new Structure named 'ST_Test', add one variable
2. Create a new Blueprint Actor
   1. Add a new variable of type 'ST_Test', compile the blueprint
   2. Set the variable's default value
   3. Compile, save the Blueprint Actor
3. Add a variable to ST_Test, save it
4. Save the blueprint actor without compiling
5. Reload the Blueprint actor (or shutdown the editor? this is what i was doing) - observe error when reopening the blueprint actor and observe that default value you set above has been lost

Expected Results:
No data loss, no error

Actual Results:
Error in log, data is lost