Recently I was met with a Tandberg TS800 (820LTO) drive which had a flashing fault LED, after some searching I found the following procedure to work
Ensure that the Fault LED is flashing amber and that the Activity LED is off.
1. Press the Eject button for at least 6 seconds so that the Ready LED is flashing (Service Mode)
2. Press the Eject button once more (Activity LED Flashing)
3. Press the Eject button twice to reset the drive (You will hear the drive resetting)
3. Press Eject once more to exit service mode
If the button is not pushed for 15 seconds, the eject button reverts back to its original cartridge eject function.