This happened to me after adding a new USceneComponent and renaming one of them. It seemed to be fixed after restoring the original name and deleting the new USceneComponent, but after a lot of changes trying to get it working, I ended up creating a new Blueprint from the modified C++ class.
Luckily they were pretty simple blueprints, but this is very annoying. There has to be a cleaner solution rather than revert everything to an older changeset. I think it’s very common to add new components via C++, and if this keeps happening from time to time…