This has been discussed so often in typology on this Board: the possibility of being born one type and changing types along the way, making for odd cognitive functions and enneagram combinations. I have an old theory on a thread here Typology Thoughts, stating that under stress, the dom or aux function will morph and change attitudes, becoming introverted (usually) or extraverted when it was in fact supposed to be the other attitude.
For example, If you were supposed to be an ENFP, your dominant function would be Ne and your aux function would be Fi. If, however, under the influence of neglect or abuse, our intuition was not allowed extraverted room to grow, it might become instead introverted, or Ni. Therefore, your personality might manifest in the world more as Ni/Fi (like Mole on here, as a classic example), giving you and odd flavor of type.
Confounding this would be enneagram and instinct nature. So an intended natural ENFP could manifest as INFJ (because the dom function is more closely aligned with INFJ, Ni), but perhaps have an enneagram supportive of the more intrinsic nature, 7w8 SX/SO.
I had originally theorized that the dom function would be the last to change, and that the aux function might be the first to give way to external stressors, but now I am not so sure about that. Since the dominant function is relied on mostly that first 7 years of life, or so, if the major traumas occurred in that time period, it serves to reason that the dominant function would be the most affected. In summation, the function most affected might be the function being predominantly developed at the time of the trauma, or stress.
Interestingly, perhaps the enneagram instinct is more deep-seated and more difficult to change than our cognitive functions. So if we are in a conundrum about figuring out our type, if we can really get a handle on our enneagram fix, then we can be pointed in the right direction of our original cognitive processes given to us at birth.