What is the authenticity of the debate that took place between Imam Al-Shafi'i and Imam Ahmad regarding the ruling on one who abandons prayer, and what is the refutation against those who use it to argue for the predominance of Imam Ahmad's view on this issue?

This alleged debate between Imams Ahmad and Al-Shafi'i regarding the one who abandons prayer is unsound in both its chain of narration (sanad) and its content (matn). Al-Subki himself indicated its weakness by saying "it was narrated," and Al-Albani confirmed that it is interrupted. As for its content, it is not befitting for Al-Shafi'i to present such a weak argument, because it is well-known in the madhabs of Ahmad and Al-Shafi'i that an apostate does not return to Islam merely by reciting the two testimonies (shahadatayn) unless the cause of their apostasy is removed. Al-Shafi'i is too great to be ignorant of this. Whoever disbelieves by denying a fard (obligatory act), their Islam is not valid unless they acknowledge that fard in addition to the two testimonies. The disbelieving one who abandons prayer does not become Muslim except by praying, because the cause of their disbelief is not removed except by it.