Windows 10 feature updates break activation, change computer name on domain PCs

We have a batch of 40 identical PCs, refurbished by an MS licensed refurbisher, who activated windows through KMS. When W10 version 1703 was installed, all PCs lost their activation status and the computer name (but not the netbios name) changed to a random string beginning with "WIN-".  They also couldn't log onto the domain, initially.  We resolved that on all PCs and assumed that would be the end of it.

But now, version 1709 is doing the same thing, except this time, it's weirdly reverting to the computer name originally given by the refurbisher (although again, netbios name stays the same).  So it looks like this will crop up every time there's a new feature update.

When the original 1703 issue happened, nobody on the net seemed to have heard of this behaviour and couldn't believe that a feature update could cause it. However, the refurbisher knew about the issue and had activation codes paired to dell service tags ready to send.

Has anybody else heard of this behaviour or have any idea what's happening or how we could avoid it in future?