UE4.12.2 bug when refactoring blueprints to C++


I am currently in the process of refactoring my code to move variables from blueprint to a native base class.

The steps i have used with success before are now unstable. this is:

  1. Start with blueprint class, containing variables A, B, C

  2. Create C++ class, and reparent blueprint class to be child of C++ class

  3. Create variable A1, B1 and C++ class

  4. Manually change references in the blueprint to from A and B to A1 and B1, and recompile

  5. Add a variable C1 to the C++ class

  6. recompile

  7. A strange error occurs within the blueprint (see screenshot for an example)

  8. Attempting to recompile or in any way touch the blueprint causes a crash of the editor - after reloading, everything is fine?

Not sure how to fix this, it’s causing regular crashing when trying to refactor…

I think it might be a regression of this old issue: 4.7.5 Hotreload BlueprintReadWrite UPROPERTY - Blueprint - Unreal Engine Forums

Hey braindigitalis-

Can you elaborate on step 3? Is A1 and B1 being created inside the C++ class? Is the C++ class created in step 3 another class separate from the class created in step 2? If so, what type of class is it? Also in your screenshot I don’t see Current Y or Current X in the My Blueprint tab, are they part of A/B/C or A1/B1/C1? Let me know if you can reproduce this in a new project and if so, please be as descriptive as possible in the steps taken to setup the bug.

Hi braindigitalis,

We have not heard back from you in a few days, so we are marking this post as Resolved for tracking purposes. If you are still experiencing the issue you reported, please respond to this message with additional information and we will offer further assistance.

Thank you.

hi, i managed to duplicate this bug and have posted a separate question, with video, stack trace and log here:


Since you have a second post with more detailed information, I will be marking this as a duplicate in order to focus attention for the issue in one place.