I meet the same issue.
I find a walkaround to select the Blueprint derived from C++ class, that is Click the wanted Blueprint in Content Drawer and then Click the button with left arrow icon.
Now, the project can run without any errors or warnings.
But, when I close the project and reopen it, I meet a new issue, as the img show:
All the setting regarding to that Blueprint became invalid, and the C++ class also became invalid.