WARNING, SPOILERS AHEAD
YOU HAVE BEEN WARNED

The two narrators in the game present two opposing views about the Qube, and in the end, the one that makes the least sense seems to be the definitive answer. But is that really true?

Let's look at both possible scenarios. Option 1, the astronaut inside the ISS is right and the Qube is an alien structure heading toward Earth. Option 2, 919 is right and the player is held captive amd forced to solve puzzles. Neither of these options can explain everything, so let's look at each one and list the facts that don't quite line up with it.

Option 1: Alien Spacecraft
1. The player wakes up inside the cube without any sort of entrance nearby. How would they have entered the cube?
2. Why did she call it deep space travel if the Qube was shown to be near the moon in the final scene?
3. Why would aliens build a spacecraft consisting entirely of puzzles? Not to mention that the symbols (arrows, play button) are understandable for a human.
4. Why is nobody except for the player inside the Qube?
5. Why are there escape pods if the Qube is unmanned?
6. Why is the Qube supposedly breaking apart if nothing is shown to be happening in the final scene?
7. How would incapacitating the Qube stop it from destroying Earth? Its direction or speed would not have changed.
8. Why is there gravity inside the Qube?
9. How would a suit create all the nutrients needed for human survival out of light? Not to mention where the excrements would go for Jonathan Burns. His box would have to be filled with it.
10. If Jonathan Burns survived because of his suit, there must be light grtting into his box. But if there was light,he wouldn't be trapped in the dark like he says and he would be able to see the outside and realize that he is in space.
11. Jonathan would also have to notice that there is no gravity, and as such he couldn't be underground.
12. Why does the player's life suit have the ability to move the blocks?
13. Why did they send a single person to dismantle an alien spacecraft from the inside? How would they even know that there wouldn't be any aliens inside that would kill the intruser and that the Qube can be destroyed from the inside?
14. Why would the player be unconscious for two weeks? What would've caused the amnesia?
15. If the player's video transmission was broken, how would the narrator know that there are escape pods?

Option 2: Underground Testing Facility
1. What is being tested? The player's equipment? The puzzles themselves?
2. Why would the testers build such a giant facility and break it?
If the testers have the ability to erase someone's memory, why would they want to kill the test subjects if they could just erase their memory?
3. How would they build things such as the magnetic puzzles that ignore gravity, the light beams, the puzzles that require the player to pick up spheres of light, and the balls and transparent blocks that can be walked through?
4. Why would the other voices keep telling lies when the player is already inside the shuttle flying toward their death without any option to return?
5. Why would the testers pretend the player's video transmission is broken?
6. What box is 919 in, how did he get there, and where did he get the equipment to communicate with the player?

As you can see, option 1 has far more contradictions than option 2, which makes me believe that 919 is actually right and the ending scene is what the testers want the player to believe. Considering that most contradictions in option 2 are simply things we don't know, it is far more likely than option 1, whose contradictions simply don't make any sense. And since the testers would be so good at faking things, they could've easily faked the ending scene too, for example by replacing the windows in the escape pod with screens.

That is only my opinion though. Let me know what you think, and please tell me if I've missed any more contradictions!