Last time we addressed the complications involved when Adam replaces himself to take his test, and we observed that there were additional complications involved. There should have been three teams of time travelers moving through the halls of the school, but somehow there was only one–and this is something that the film does fairly consistently but which does not appear to have any logical basis: if a time traveler travels to the same coordinates twice, he replaces the previous time traveling version of himself. Thus when team two arrived at the high school, team one vanished as if they were never there, and team three likewise caused the elimination of team two.
This seriously complicates the problems we noticed last time. Not only do the original Adam and the Adams from teams one and two not hear the questions that the team three Adam has to answer, part of Adam’s life has been erased completely. That is, we have a sequence something like this: Adam fails the test; Adam travels back and prevents himself from taking the test, and then attempts to answer the questions his younger self has never heard; Adam travels back and erases the version of himself who took the test such that he not only never took the test, he never existed and will never fail the test and make the trip back to retake it; then Adam fails the test again, and again travels back to erase the version of himself who failed the test such that he, too, will never have failed the test. It would seem then that Adam must have failed the test in the original history and then replaced that history with the fourth attempt in which he passes it–but even though Adam replaced himself in the past, it does not seem that he replaced himself in the future. Thus we ought to have Adam leaving Monday at one, then finding himself back getting an answer to a question he was never asked and leaving again at two, then again finding himself back getting an answer to a question he was never asked, and then leaving again at three. He has erased from his own life the events that lead to his actions.
The film took the notion of interacting with your doppelganger very seriously, too seriously; but then they step into a very serious complication using the replacement rules from The Butterfly Effect franchise (which were incomprehensibly disastrous in those films), applying only when the time traveler replaces a time traveling version of himself. That is a far more serious interaction with a past version of yourself than merely letting him see you, but the film glosses it without even attempting to provide a suggestion either for why it would work that way or for why the time travelers would expect it to do so. It was poorly considered, and a major problem with its time travel concepts.