Answer: Who can guarantee that a Kabbalist understands what he learns? Only a person who is present in the classes can determine if the teacher understands and is familiar with what he teaches.
Question: Are there any external signs you can use to determine if a person understands the wisdom of Kabbalah or not?
Answer: None! Baal HaSulam observes only indirect signs: a recognized teacher who is teaching according to the true sources and doesn’t tie the students to himself. It cannot be otherwise.
From the Kabbalah Lesson in Russian 9/24/17