Imaging issue DeployStudio
This isn't directly related to what @fsb suggests because this issue is caused by the fact the machine needs a firmware update, this is part of the usual install process of High Sierra, but if you've been using images it won't have the Firmware update.

There are some steps to try on this website which I myself am trying now...

https://www.amsys.co.uk/deploying-firmware-updates-imaging/