None of the above.
The Voyager project science team is in agreement over what is meant by leaving the solar system, knows exactly where the spacecraft is, and has been very careful what they say about all this in their declarations over time. Nevertheless the news reporting would simplify the findings to something like "Voyager 1 has left our Solar System!", since that's easier to understand than "The Voyager 1 spacecraft has reached a distant point at the edge of our solar system where there is no outward motion of solar wind." or "The stagnation of this solar wind has continued through at least February 2011, marking a thick, previously unpredicted 'transition zone' at the edge of our solar system." So there have been many news reports of Voyager 1 leaving the solar system over the past three years, when in fact the actual press releases were rather more specific. In their September 12, 2013 press release, they said for the first time "Voyager 1 Has Entered Interstellar Space".
Voyager 1 has left the solar system, defined as crossing the boundary between the plasma that comes from our Sun and the plasma in interstellar space. It turns out that there is a clear boundary where the pressure from the solar wind and pressure from the local interstellar plasma wind balance. At that boundary, there is a significant jump up in plasma density when you move into the interstellar plasma.
On the 25th of August, 2012, Voyager 1 measured very abrupt changes in the local environment. This was in fact Voyager 1 crossing the heliopause. In a single day. Unfortunately, they only saw two out of the three expected signatures of having crossed the heliopause. So being the conservative sorts they are, they did not declare a crossing.
The kicker was that the magnetic field direction only changed by 2°. They were expecting a much larger change, based on models of the direction of the local interstellar magnetic field. This was a puzzlement. Since they did not have a direct measurement of plasma density (due to the failure of an instrument much earlier in the mission), the science team was left in a state of uncertainty about whether or not they were really in interstellar space. From an August 2012 press release:
Scientists eagerly awaiting the entry of the two Voyagers into interstellar space have recently seen changes from Voyager 1 in two of the three observations that are expected to be different in interstellar space. The prevalence of high-energy particles streaming in from outside our solar system has jumped, and the prevalence of lower-energy particles originating from inside our solar system has briefly dipped, indicating an increasing pace of change in Voyager 1's environment. Voyager team scientists are now analyzing data on the direction of the magnetic field, which they believe will change upon entry into interstellar space.
By sheer luck, a large coronal mass ejection from the Sun tickled the plasma around Voyager 1 a few months later. The resulting ringing allowed them to indirectly measure the plasma density, which matched what was expected for the interstellar space in the vicinity of our solar system. They were able to find earlier, weaker oscillations, extrapolated back, and found that the density increased very rapidly in, you guessed it, August 2012. That provided the confirmation they were looking for.
The magnetic fields were expected to have different directions since they have different sources. There would be no reason for them to have the same direction, so that would be unlikely.
But, not impossible.
In short, there was a very sharp change when crossing the very real heliopause. The determination that that really was the heliopause was delayed by an unexpected approximate alignment of magnetic fields.