Breathe deep and try to relax. Everyone misses the fact that Abe built the boxes but pretended to still be developing the experimental machine with Aaron. This does not mean that Abe has traveled yet. He may not have used it yet, he may not even realize completely what it does. It only matters that it is in working order and that it is turned on. If your best friend is impulsive and not fully trustworthy, wait. Don't tell him everything. First learn as well as establish the ground rules and safety policies. Insure your survival as well as the invention itself.
We can now arrive at the first major time line where Abe builds the fail-safe box, sets the timer, and unbeknown to Abe,Aaron(2) pops out. That leaves Aaron(1) with four days to find the fail-safe and disappear. However, for this wound in the fabric of time to heal and for Aaron(1) to disappear as in the first play of the time line, all events must continue as before. If there is a serious deviation, if Aaron is interfered with or if Abe moves, locks, or turns off the box; then that time line will be forever altered. It doesn’t matter if Aaron brings the other box on this trip or not. He only needs to gain the upper hand, to gain control, to arrive first. He can always reemerge later with the folded-up box as long as he does so before Abe figures out that Aaron(2) is around. If Abe figures that out, he could fail-safe and move the box to a secret location, which would leave Aaron(1) stranded with no foreseeable exit window.
Once Aaron gets to the point where he exits the fail-safe and turns it off, he will gain control of the Primer universe. At most, Abe can only travel back in time 15 minutes later than Aaron (because of the 15 minute delay switch). A few hours window would even be better. You could fail-safe, turn the box off, take a long nap, and then activate the delay timer. Thus, you arrive several hours before your friend or foe returns. It would appear that Aaron may have left the box on the first time. But quickly, he plots to have his own box and recognizes that turning the box off is a much better means of control. We can explore this idea and its consequences later.
Aaron thus creates a new time line, one that is untethered from the original. The original time line has been lost forever, that is, the box cannot be used to enter into a time line where time travel does not exist (as was the case in the original time line). Abe will later regret this when he sees what a mess the time line becomes, thanks to Aaron's impulsive decisions. Abe wants to go back in time, exit, and disable the box. However, this serves no purpose if Aaron(2) is there with his own box hidden somewhere.
Aaron(2) must behave as Aaron(1) would anytime he is around Abe. He also must insure that Aaron(1) finds the fail-safe and gets in to avoid a paradox that could erase his existence.(This is obviously what Aaron acknowledges although this does not necessarily mean that he could not survive a paradox) Aaron will have to try to speed things up with helpful assistance since Abe is stalling on his progress on the experiment so he has more time to work on his box at the U-Haul. Abe and Aaron both need each other in these early stages. The power of time travel though, has already unraveled their trust in one another. Both of them have become selfish, secretive, sly.(In fact, from some perspective Aaron(2) and Abe(2) may both have influenced, unseen to us, the events we see, be it Aaron(2) speeding things up or Abe(2) attempting to thwart Aaron's efforts, even those of Abe(1).
