I managed to find a workaround, it is not pretty, but it worked for me. This might be suitable just for one/two classes not for many.
- Before changing the parent class in c++ - reparent your blueprint’s parent to AActor, save.
- Make your changes in c++ class, compile, run.
- Reparent your previously reparented class to your newly changed c++ class.
This worked for me. As I said It is not pretty but it worked for me. Might help someone. Have a good one.