Check to see that you have the correct View Agent and options are installed. I recall running into an issue when I was doing upgrades of the View Agent and removed it but did not reinstall it in a timely manner. The View Composer thought the link-cloned system was bad, deleted it, and provisioned another one in its place.
If that is all good then it is possible that the domain join is failing. Check to see of the computer object is being created in the OU that you are joining system to. As you stated, you added the service account into the Domain Admins group... so if you are not seeing the computer object being created and deleted, then it may be that your VDIs are having issues with resolving the DC during the domain join. I ran into this issue when we had DNS issues, my work around was an ipconfig /renew on the systems before the domain join. While an ipconfig /renew may not be possible to script in this scenario, you can tweak your DHCP settings as needed (set the Primary DNS to a DC that you know you can join systems to and, if needed, confirm that you set the suffix search list).