Problem upgrading from 2 bay to 4 bays

#1

Had bay 1 & 2 with 4TB discs each in RAID 1 (Vol 1) which became full eg over 95%. I have since deleted 1.3TB
Added a 4TB to each of bay 3 & 4
Seems made the mistake of asking Vol 1 to expand expecting it to add the 2 new disc.
Now stuck with red LED on disc 1 with the display telling me to replace it and the Dashboard telling me it is expanding and to replace disc 1 and that Vol 1 is degraded. All disks are shown as good.
Tried robooting and putting one of the new discs in bay 1 but still get the same display.
Tried changing to RAID 5 which I think would be correct but that wants to reformatt all discs and there is no option to migrate.
Could anybody offer any advice?

#2

Hello ColJenWD,

You can refer the link provided below for more information on RAID migration.

https://support-en.wd.com/app/answers/detail/a_id/20862