If a custom code class is modified and a Hot Reload performed, any existing unsaved Blueprints derived from that class can no longer be saved.

When a custom code class is changed and a Hot Reload is performed, any Blueprints previously made from that class can no longer be saved.

Possibly related to [Link Removed].

WORKAROUND:
Close and re-open the Editor.

1. Create a new code project using the First Person template.
2. Add a new code class to the project that derives from Actor.
3. Close the Editor.
4. Add the following UPROPERTY to the new class header file:

   UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = TestCat)
   float MyFloat;
   

5. Build the project in Visual Studio.
6. Open the project in the Editor.
7. Make a new Blueprint deriving from the class created in step 2.
8. In the new Blueprint's Event Graph, create the setup shown in the attached HotReload image.
9. Compile the Blueprint, but DO NOT SAVE it.
10. In the header file for the class created in step 2, add the following line of code: int32 a1, a2, a3, a4, a5;
11. Click the Compile button in the Editor.
12. In the Blueprint, click Save.

RESULT:
The following error message is displayed:

Can't save C:/Users/Tim.Lincoln/Documents/Unreal Projects/TestHotReload1/Content/FirstPerson/Blueprints/MyActor_BP.uasset: Graph is linked to private object(s) in an external package.
External Object(s):
HOTRELOADED_MyActor_0
/Engine/Transient
  
Try to find the chain of references to that object (may take some time)?

EXPECTED:
The Blueprint saves successfully.