Hello, Rudy!
I have also got double MyBlueprint tabs on several occasions in addition to the unrecognized tab:
I have placed them underneath each other in this screen shot. This is from a Widget Blueprint in a new C++ project without anything else added or modified. The Widget Blueprint and the Designer is empty! I am not sure what triggers this but it does not happen every time.
For me the unrecognized tab shows up after using the blueprint editor for some time. I’ll document it properly the next time it happens!