"shema yigrom hacheit" - can a navi have doubts?

Ya’akov approached his encounter with Eisav with fear and trepidation, “Vayirah Ya’akov m’eod vayetzer lo.” Although he had been given an explicit promise of protection from G-d, which Ya’akov invokes here in his prayer, “V’atah amarta heitev eitiv imach v’samti es zaracha k’afar ha’aretz”, Chazal say this even an explicit promise from G-d is insufficient as a guarantee of protection, as “shema yigrom hacheit”, G-d's promise is ultimately predicated on the continued goodness of the recipient, which may change over time. As discussed previously, the Rambam distinguishes between personal promises to a Navi, whose fulfillment depends on the Navi’s level of righteousness, and prophecy which the Navi is told to openly declare, which is guaranteed to be fulfilled.

The Rambam in Shmoneh Perakim (ch 7) writes that a Navi need not have perfect middos, as we find in Tanach many examples of Nevi’im who do fall victim to sin and spiritual shortcoming (albeit minor points in the scheme of their overall personality). One of the Rambam’s examples is the fear Ya’akov displayed in his encounter with Eisav – given a direct promise of protection from G-d, Ya’akov’s actions reflect on some level a shortcoming of belief in this Divine Protection.

Achronim are struck by the contradiction in the Rambam: on the one hand, the principle of “shema yigrom hacheit” indicates that Ya’akov’s fear was justified, and he could not rely on a private promise of protection, yet on the other hand, the Rambam sees such doubt as a shortcoming of Ya’akov and a lack of bitachon. Which approach is correct?

Two suggestions, one easy, one hard. The Bais haLevi asks, if indeed the promise of G-d is not guaranteed, why does Ya’akov invoke it in his prayers? He answers that Ya’akov was not appealing to the terms of his personal promise but he was appealing to the concept of chilul Hashem. True, fulfillment of G-d’s words ordinarily should depend on personal merit, but here, if Eisav were to win out it would not just mean a loss of face personally for Ya’akov, but a repudiation of the entire Torah lifestyle which Ya’akov represents. This Ya’akov finds intolerable. Perhaps this solves the discrepancy in the Rambam as well. Ya’akov’s personal fear was indeed justifiable, “shema yigrom hacheit", as one can never be sure that one is on the level of meriting fulfillment of Divine promise, but to fear and doubt that the Torah lifestyle would ultimately somehow emerge victorious should not have been part of Ya’akov’s response and was on some level a shortcoming.

An easier answer might be that the promise to Ya’akov, as he states in his prayer, included a guarantee to his children – “v’samti es zaracha k’chol hayam”. While Ya’akov may have been justified in fearing his personal merit was insufficient to guarantee fulfillment of G-d’s promise to himself, there is no reason for him to have assumed that his shortcomings would affect the fulfillment of G-d’s guarantee to his children and to doubt their safety and security.