I went into the BIOS and disconnected the battery as per the provided guide. When I tried to start up again, the laptop did not turn on properly and the LED flashed at me.
The power button turned on, then off again, and the lights flashed as follows:
So positions 4 and 10 after the white were red, meaning CPU deassert sleep S4 and CPU reached S0 state.
Additionally, plugging the power adapter in causes the LED to light up white, as normal.
Not sure what else I can do. Any help would be appreciated.
Edit: issue resolved after disconnecting RTC battery.