logical deduction - The Numberphile Heist (part 1)

Hello Puzzling Stack Exchange! While part 1 of the PSE School of Enigmatics remains unsolved, I've got part 1 of another puzzle series for you to solve. I'm in no way affiliated with Numberphile; however, I am highly appreciative of the channel, and find their content to be invaluable. Enjoy!

URGH. You've run out of brown paper; and, quite frankly, there's only one way to get more - crack open the Numberphile vault.

Sneaking your way past two security kangaroos, you make your way to the vault.

You notice that the buttons 2, 4, 6 and 8 are located on hinges. You carefully pry open these buttons, and find yourself with a sudoku-esque conundrum:

Hmm. How hard could this be? You punch in 314159265, the first 9 digits of Pi, and immediately you are startled by the sound of grinding as the nearest missile launcher points at you. One more failed attempt, and you're toast.

You try prying open the other buttons, but to no avail. However, you do notice that the 5 button is written funnily, and pops out of the display. You can't pry it open, though.

What could the password be?

Hint 1

Can the sudoku actually be solved?

Hint 2

Yes, the sudoku can be solved. But then again, even a sudoku puzzle consisting of an empty board can be solved.

Hint 3

Perhaps if there isn't one solution to the sudoku, could the puzzle have to do with more than one of its possible solutions?

Answer

It has been four days since you encountered this door, and it has stumped you. You are hungry, have to use the restroom, and regret not simply turning around and buying more brown paper at Brown Paper Mart™

No. You can beat this. You hear the voice of the hint fairy whispering in your ear "don't solve the sudoku, just look at the branches of possibility to solve it". Maybe that's delirium from the hunger? You don't care, you trust it either way.

The 5 button stands out, literally and figuratively. It must mean something. Perhaps if we were to draw a grid from the other grids...it becomes a complete grid, with 5... or whatever this odd symbol is, in the middle.

Then we just use our old sudoku logic to fill out what we can.

That's what we can get with no assumptions outside of thinking we know the middle number in each square. So the password?

193451789 The buttons themselves tell us the order to input it.

Well, it's either that or

The keypad is a ruse and the door was unlocked. I mean, there is no enter key, after all.