G-SPEED Shuttle XL Tunderbolt 3 evSeries Red LED

My Shuttle XL in RAID5 has shown a red LED on bay 3 and the drive is flagged as ‘dead’. I have read this could be a false positive - if this is the case, how do I fix it?
If the drive is actually dead, how do I go about replacing it?

Do I have to rebuild the RAID5 from scratch?

You only have to rebuild the RAID5 from scratch if you used the unit while it was marked as dead. If you have made no changes then you can just put the drive back online and continue using the unit.

GSU reporting DEAD drive