Check the references of the three files in question (right click them in the content browser and hit the show references button). If the parent is aware of the child class (possibly even indirectly), you’ll have a circular reference. If this is the case, you can likely work around it by using interfaces or inheritable functions in the base class. If it’s not the case, I’m not sure what else is the problem and the Epic team might have a better idea on how to help you out 
As for updating, ideally, you would never change the dialogue system files and instead only inherited from them. If you haven’t changed the base files, you can update by simply migrating over the new files, if you have then anything you’ve changed in the base files will likely be lost while updating (there’s no way around this AFAIK, BP assets can’t merge differences unfortunately).