Storage Spaces - Virtual Disk Degraded but all Physical Disks OK.

I have a thin provisioned virtual disk comprising of three physical disks that is showing as degraded:

PS C:\> Get-VirtualDisk "Data" | fl FriendlyName,*Status

FriendlyName      : Data
OperationalStatus : Degraded
HealthStatus      : Warning

PS C:\> Get-PhysicalDisk

FriendlyName        CanPool             OperationalStatus   HealthStatus        Usage                              Size
------------        -------             -----------------   ------------        -----                              ----
Disk 1              False               OK                  Healthy             Auto-Select                     2.73 TB
Disk 2              False               OK                  Healthy             Auto-Select                     2.73 TB
PhysicalDisk0       False               OK                  Healthy             Auto-Select                       40 GB
Disk 3              False               OK                  Healthy             Auto-Select                     2.73 TB

When attempting to repair the disk with "Repair-VirtualDisk" the process errors out at 0%:

PS C:\> Repair-VirtualDisk "Data" -Verbose
Repair-VirtualDisk : Failed
At line:1 char:1+ Repair-VirtualDisk "Data" -Verbose+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : NotSpecified: (StorageWMI:ROOT/Microsoft/...SFT_VirtualDisk) [Repair-VirtualDisk], CimEx
   ception+ FullyQualifiedErrorId : StorageWMI 4,Repair-VirtualDisk

I can create a new virtual disk in addition to the existing one on the same three disks and no health warnings occur. I have installed KB3000123 and KB 2914743 which have been recommended elsewhere but saw no improvement.

I'm keen to avoid having to move the data to a new virtual disk, or backup and restore.