For mixed artifact projects that use external assemblies as references, when the projects are built as release and deployed using the server configuration, the deployment fails because the "schema" (mixed) assembly is deployed before the external assemblies and BtsTask fails.
Based on suggestions from a few forums I've called the "DeployExternalAssemblies" target from the "CustomDeployTarget"
For mixed artifact projects that use external assemblies as references, when the projects are built as release and deployed using the server configuration, the deployment fails because the "schema" (mixed) assembly is deployed before the external assemblies and BtsTask fails.
Based on suggestions from a few forums I've called the "DeployExternalAssemblies" target from the "CustomDeployTarget"