I have tried the HPD6(D) firmware update in Windows but it reports:
Update not attempted (or interrupted). All selected devices are either up-to-date or have newer versions installed.
However, in HPE Smart Storage Admin it only reports the firmware version is HPD6 and not (D). The firmware does say: "Customers who already installed firmware version HPD6 do not need to update to HPD6 (D)."
I will have to try reseating the drives after hours.