The issue is that the book and comic both cut Finn saying it's impossible, but keep Finn describing the tracker room by name. The book was released two months after the movie. I don't think it's a stretch to say that they did this on purpose, especially when there are other retcons along the same lines. If Finn doesn't call it impossible, there's not an issue, beyond the continuity issue of shutting the breaker down becoming shutting the tracker down.
OK, I’ll just be honest and admit I am not getting what your issue is here. At the beginning of the movie,
all of them believe that tracking is impossible - but they admit that that is exactly what is happening to them. Therefore it is apparently new tech, and Class A. Finn surmises that it must operate like all other similar Class A tech and have a main breaker somewhere, and states that he can lead them to the location of the breaker. Just because he later uses the word tracker (and, as you point out, he appears to refer to the location of the tracker* once he’s on the ship) – how is that affected at all by the fact that he
initially thought tracking was impossible?
What about in ANH? Everyone in the Falcon refused to believe that the Death Star was anything other than a moon - even after seeing it with their own eyes - because it was supposedly impossible for a battle station to be that big. (Same, BTW, for the destruction of Alderaan - the characters called it impossible.). So, when they start referring to locations on board the Death Star, and ultimately lead an attack mission against it – is there a plothole just because they once stated that the mere existence of it was impossible? No, because, however impossible they may have initially considered it, they had proof that it was not impossible, and the story moved on from there.
* (Heck, I’m not even sure that the distinction between the breake and the tracker is even a real glitch after all - the script only says that the tracker is
controlled from the bridge, not located there ( if I mistakenly use the word located in an earlier post, that’s my bad) and it could be shut down by turning off the main breaker. I don’t think there’s anything in the script that stated that the breaker and the tracker were not in the same location – only that the only two ways to
turn off the tracker were via the controls on the bridge or at the breaker. It may very well be that the breaker and the technology it controlled were customarily close together – making “breaker” and “tracker” interchangeable as a reference to the location for someone knowledgeable about how the breaker system worked on board these ships.)