It will depend on a few things how a “failed” is determined.
Ignoring the complexity of a Custom Success Criteria, a fixlet must go non relevant (its targeting relevance needs to go false) and a task must complete all lines of the action successfully.
An action that is running when the client is restarted (or the OS is restarted) will also fail by default as the interruption of the action is considered a failure.
Custom success criteria can change all that but its a much more complex case and may not be involved here.