Jung considered all of the functions that were not yet differentiated to part of the "shadow."
If one adopts the function orders that are commonly used (e.g., INTJ = Ni, Te, Fi, Se), then these "loops" have nothing to do with the shadow, but might involve an undifferentiated function. After all, INTJs don't appear to have "Si+Ti" issues. So, continuing with the INTJ example, then Ni is differentiated, and Fi may or may not be differentiated. The "loop" concept comes from neither Ni nor Fi being extroverted, so if the "solution" to the "Ni Fi problem" lies outside of oneself, one will continue to "loop" internally, never arriving at a valid conclusion. Similarly, for ENTP, if the solution to an "Ne Fe problem" lies inside of oneself, one will continue to "loop" externally, never arriving at a valid conclusion. In most modern MBTI theory, the "problems" of a type lie in the lack of differentiation/development of the auxiliary function (Te for the INTJ), which means that one is either extremely introverted and thus lacks a reasonable grounding in objective reality, or extremely extroverted and lacks self-understanding.
If one actually differentiates the functions involved, the "loop" aspect disappears. Ni+Fi can be a source of (subjective) wisdom, balanced by solid Te logic, and Ne+Fe can be a strong empirical appreciation of people, balanced by an internal Ti ideal.