Is the chain of transmission sound despite the aspersion on 'Ikrimah and Dawud's delusion at the end of his life?

Al-Nasa'i narrated with an authentic chain of transmission from Ibn Abbas the story of a man from the Ansar who embraced Islam, then apostatized, then regretted and asked about his repentance. Thereupon, the verses from Surat Al Imran (3:86-89) were revealed, which speak of Allah not guiding those who disbelieved after their faith, except for those who repent and reform. So the man returned and embraced Islam. This hadith (definition) is authentic, with no blemish in it, and it has other supporting evidence. These verses indicate that whoever knows the truth and rejects it is punished by relapse, unless Allah makes an exception for the repentant reformers. As for one who disbelieves and dies upon their disbelief, they have deserved the punishment.