Two shells are generally used when administering the Bluecoat X-Series hardware, admin and root. Admin is generally used to log into the CLI to configure XOS. Root is generally used to log into Linux and administer it.
If a change is made to the admin account's default shell, the user will not be able to get into the CLI and instead will always see the Bash shell. The admin user is basically locked out of the CLI with no XOS commands available. To verify this is the issue that you are having, you can run the following command as admin from the Linux shell: