I just ran across this issue today. We are running XOS 30.2.0.29 and XMC 8.5.2.6.
I moved a switch from one policy domain to another and tried to Enforce but got an error. The issue ended up being a case difference in VLAN names.
On the switch, vlan 1123 was named vsh-1
On all other switches and in the policy, vlan 1123 was named vSH-1
I tried renaming the vlan - config vlan 1123 name vSH-1 - but was told it already existed by that name.
I then fixed the issue by renaming the vlan to something else, then to the uppercase name.
No more Enforce issue.