A pure devotee is always praying for protection not to fall down.

There is only "one" class of jiva-souls who can be either nitya-siddha or nitya-baddha.

The comment in Caitanya Caritāmṛta claiming there are two types of jiva-souls, really means you are nitya-siddha while in Vaikuntha, but in the material worlds you are nitya-baddha. 

Prabhupada explains here,

Srila Prabhupada - "The actual constitutional position of every marginal living entity is nitya-siddha. By following the rules and regulations and instructions of the spiritual master, the jiva-soul can become AGAIN nitya-siddha. So the Krsna consciousness movement is to make the nitya-baddhas AGAIN nitya-siddha." (NY City Lecture on CC, July 13, 1976)

All jiva souls are originally nitya-siddha but because they have free will, they can choose to fall down into the material worlds.

There are foolish gurus and sannyasis out there who believe a class of jiva-souls can never fall down, such an idea is nonsense because that means they have no free will.

Free will means to be able to do right or wrong otherwise you have no free will.

Only Visnu-tattvas expansions and those jiva-souls who CHOOSE  not to fall down, never fall down from Vaikuntha and Goloka-Vrindavana but any jiva-soul who are nitya-siddha in Vaikuntha and Goloka-Vrindavana CAN fall down at any time if they choose and become nitya-baddha.

There are fools out there who claim "not even the leaves fall from Vaikuntha"

Such a silly nonsense idea believed by bogus gurus is nonsense.

A pure devotee is always praying for protection not to fall down.

Once, in a lecture at Bhaktivedanta Manor, Srila Prabhupada said, “All of you can fall down, but I cannot fall down.” 

After the lecture, Srila Prabhupada came before the Deities and was praying, and later one disciple asked him, “Srila Prabhupada, what were you praying?” 

Srila Prabhupada replied, “I was praying that I may never fall down.” 

The disciple, astonished, objected, “But Srila Prabhupada, you just said that you cannot fall down.” 

And Srila Prabhupada explained, “Yes, because I am always praying that I may never fall down, therefore I can never fall down.” (From Giriraj Swami essay, "Srila Prabhupada arrival in America")*