@kratkale I’m confused what you mean their serial numbers are erased?
FOG isn’t overwriting the serial numbers on these devices.
Furthermore, Serial numbers aren’t stored directly on the host, they’re stored on the inventory table.
That column (hostDevice) is about storing what device a host will be using to image against.
If somebody is updating the group, the empty hostDevice (Group device for groups) would likely be overwriting it.
I’ve pushed a code change to hopefully address this particular issue in the latest dev-branch.