The JCR view tool is configured to be automatically opened when entering the repository workspace.

    <default>
        <uitool-factory id="uitool-repository-jcr"/>
    </default>

This should not happen when a maintenance is running because the repository is unavailable. A solution could be to not automatically open this tool if the application is in safe mode. This is already done for the admin workspace, where automatically opened tools are not the same depending on safe mode.