For anyone that may come across this post in the future: This was acknowledged as a bug and resolved (supposedly for all customers) by AirWatch support.
Thank you for letting us know. However, I just received the same error with some iMacs of ours.
The iMacs were DEP:ed and thus added to our WS1 console with Default Staging User as User for those devices. I can't change that though. May that be the issue?