My volume down button randomly stopped working, and then randomly boots to "*** LOCKED ***" screen

[Dassauce]

My volume down button randomly stopped working, and then randomly boots to "*** LOCKED ***" screen

I'm left at a screen that says:

*** LOCKED ***
M7_WLV PVT SHIP S-ON RH
HBOOT-1.61.0000
RADIO-1.13.41.1209
OpenDSP-v35.120.274.0718
OS-6.22.605.6
eMMC-boot 2048MB
Nov 30 2015, 16:34:38.0

HBOOT

<VOL UP> to previous item
<VOL DOWN> to next item
<POWER> to select item

FASTBOOT
RECOVERY
FACTORY RESET
SIMLOCK
CHECK SMARTSD
IMAGE CRC
SHOW BARCODE

I apparently am unable to press the power button to select any of these options like it says to. My volume down button doesn't work, but I'm still able to navigate the menu using volume up. I randomly turned it back on and it was in Safe Mode, so I was able to access my phone for a temporary amount of time until I figured I could perhaps restart my phone to exit Safe Mode. Needless to say, I'm unfortunately back at this screen.

Are there any fixes?

I have no clue why my volume down button no longer works, nor do I know why I can't select any of these options despite my power button working fine.

Edit:
I thought this might be relevant: the phone is NOT rooted.

Also, this issue began just under a week ago.