So Windows 10 1803 update creates another OEM partition. In my case, the new partition decided to take over one of my existing drive letters, G: that was mapped to a shared network location. This was confusing, because my G drive (4TB) suddenly became empty.
Disk Management revealed what the culprit was. The All New OEM partition 450 MB in size, NTFS file format, allegedly. At this stage, I was not interested what this partition does, but what is the point of it in the first place if it's empty. All I wanted was to get my real G drive back.
What we want to do now, is to remove the letter G from the partition. In order to do this, click Start button and type CMD, then right click on it and click Run as administrator
In CMD, type:
In Diskpart, type:
select volume 3 In my case, the drive I'm interested in is a Volume 3 - G drive.
The letter G has now been removed from the OEM partition. I was now able to map my network drive to letter G again.