HX99G can't get into bios

(I would post this in the r/HX99G sub but it seems to be closed for submissions.)

For context, I've been having problems with random shutdowns on my HX99G. Not during gaming, totally random (just had one on the log in screen). I decided to install the latest bios from the minisforum site to see if that would help, and it seems to have installed correctly, but when I try to enter the bios pressing F7, I see the boot menu flash on the screen for a second and then it goes back to the Minisforum logo. If I press delete, I see the grey bios screen flash, then the same thing. Using the Advanced Recovery options on Windows or shutdown /r /fw just reboots normally.

I've seen people suggest connecting a monitor via USB-C. I don't know if that would help in my case since I do see the screen flash for a moment, so I'm guessing it's not a display issue, but anyway USB-C video output hasn't worked for me for a while (connecting any adapter prompts a "Display Connection Might Be Limited" error).

Any ideas would be appreciated!