Acer Aspire A315-53G-3967 shuts down by itself; needs key pressed to remain on

Model: Acer Aspire A315-53G-3967

OS: Windows 10

RAM: 4+8 GB DDR4

CPU: Intel i3 7th gen

What happened: I was browsing Reddit while the laptop was unplugged. When I plugged in the charger, the laptop just died on me. I tried multiple times to boot it up; it got the Acer bootup logo, but would die after a few seconds. The charging light stayed on without any problems if it's plugged in.

I also realized that when trying to boot it up, literally any other button works except the Power button. I can't confirm if plugging it in also causes problems because I can't isolate the charger without stopping keyboard presses, and stopping keyboard presses just shuts down the laptop. I have tried plugging it in while the laptop is on (and while something is pressing on the keyboard) and there seems to be no problem.

You can see videos here. The first video shows how the Power button doesn't work. The second and the third ones show that the laptop dies as soon as it stops receiving keyboard input (with or without a charger).

So yeah, I think this problem started when I plugged the laptop in, but since then, it's been causing me problems whether the laptop is plugged in or not. So far, I haven't seen any problems with bootup, memory, or the HDD. Everything's fine until the laptop thinks I haven't pressed a key in 5 seconds. I also hear the sound the laptop makes when you hold the Power button to force a shut down whenever it shuts down by itself, if that means anything.

The warranty on this laptop has expired, and all of its software are up to date.

Steps I have tried:

• Turn it off and on again
• Make sure that it actually shut down, not Sleep or Hibernate
• Turned off the laptop and held the Power button for 30 seconds
• Opened the laptop and unplugged the laptop's battery (not the CMOS). I can't do a CMOS reset because the CMOS is plugged in quite tightly and I didn't wanna risk breaking anything.
• Held the Power button for 30 seconds while the battery is unplugged
• The pinhole reset method
• The pinhole reset method for 30-60 seconds while also pressing and holding the power button.
  

The situation now: If I need to use the laptop, something has to be pressing on the keyboard at all times. I placed a jar on top of the numpad, and attached an external mouse and keyboard. It's not exactly the most sustainable setup. The Power Button options ("What do you want the Power Button to do?") screen also constantly appears whenever I remove the jar, and then the laptop dies quickly. I strongly theorize that the laptop thinks I'm constantly pressing on the Power button and pressing any other key on the keyboard interrupts the supposed input from the Power button.

Is there any way to fix this? I'm also curious if this is a motherboard or a keyboard problem.