Steady yellow light is produced by the hardware charger chip operating autonomously. This usually happens when the battery is too low to boot the system. When the cpu starts and loads the bootloader, it puts the charger under software control, at which point the led becomes flashing yellow.

If software doesn't give the charger any commands for 32s, the charger hw resets and goes back to autonomous mode with steady bright yellow led.

That it goes back to steady yellow suggests something hangs pretty badly during boot, and that the device has sustained serious damage from the drop.