After a Customer Survey task reaches a time out, the task is removed but the status will still be reflected as 'Survey Sent', with completion percentage at 50%.
Timeout actually does work but the component that should capture the timeout path is misconfigured.
This issue is fixed in ServiceDesk 7.6.
As the Customer Survey project (SD.CustomerSurvey) is open for modifications, this issue can be fixed by modifying the project.
As with any project modifications, this should be tested before putting it into production.