Virtual Disk Service Error

We use a diskpart script to configure the hard drives in Dell Latitudes (7280 or 7480) for imaging them to Windows 10. This has worked flawlessly on most, if not all, of our Dell laptops.

This is the script:

select disk=0

clean

convert gpt

create partition efi size=500

format fs=fat32 quick label=System

assign letter=S

create partition msr size=128

create partition primary

format fs=ntfs quick label=Windows

assign letter=C

Now all of a sudden, I see this error :

Virtual Disk Service Error

The specified drive letter is not free to be assigned.

It appears the issue may be happening on just one of the Dell 7480 laptop. Other machines I just imaged

Has anybody seen this error when provisioning a Dell laptop to Windows 10?