Unexpected error during publish: Sequence contains more than one matching element

This error occurs when a server name is typed in the Assemble add-in server field more than once.

To resolve the issue:

1. From Windows Explorer, go to C:%localappdata%\Assemble\.
2. Delete the Connections.xml file.
3. Publish your model. You'll need to re-enter the server name.

In future publishes, make sure to always select the server name from the drop-down list. You do not need to retype it.