Yes, I have tried several times to subscribe myself and it always go through.
The list was started as single opt-in and I have never changed its type.
I just deleted 27 unconfirmed records for the last 48 hours.
I tested further in entering an already in the list email and no name and I got this.
It gave me an Unconfirmed record.
Entering only the name gives me the same form and another Unconfirmed record.
So, the problem comes from this obviously.