Answer: Yes, there has been. Even Baal Shem Tov describes how he experienced a descent along with his servant. At that moment, he shouted to the servant: “Start reading something, say something!”
He could not do anything either because he had lost his spiritual level. Then Baal Shem Tov asked him: “Say at least what you remember!” The servant replied: “I only remember the alphabet.” Baal Shem Tov asked: “Say the letters of the alphabet!”
Can you imagine a descent of such great sages where they even forgot the alphabet? This is a complete shutdown.
Question: Now I understand why all these years people were not allowed to engage in Kabbalah. But, in my opinion, this should not happen today?
Answer: No, today it is generally unrealistic. Such special conditions were given only to very sublime souls. This is aerobatics, like a loop-de-loop for a pilot.
From Kab TV “Fundamentals of Kabbalah,” 3/27/19