Unable to remove host server from Agent Management. (4254258)

When trying to remove the host server from MMEX migration database I'm getting the following waring in EMWMigration.log:

Warning                MMExViewCore|Quest.MigrationManager.Exchange.View.AgentHostsList._removeCommand_Execute\tWarning: Agent host "[Agent_host_name]" cannot be removed, because it is involved in the migration process. Delete all associations with this server in mailbox and calendar synchronization collections, and delete it from the default agent host option in Exchange server properties.

However, this server is not involved in any synchronization job, is not added as a default host server to any of the Exchange server and is not and Exchange server itself.