There is a limitation of Bamboo where you simply cannot operate from a local user directory and a Crowd user directory at the same time. This is in contrast to the other Atlassian applications where both local & crowd user directories can be selected to both allow authentication in the one application.

I have set up Atlassian Apps such as Crowd, Bitbucket & Jira with Crowd set up for Single sign-on and user identity across the Apps. Each App has been set up with a local admin account in order to have a local account for set up and configuration and also to get access to the app if the Crowd Service goes down. However, this is not possible with Bamboo so we have had to rely solely on Crowd for access Bamboo.