Salesforce Surveys: "An error occurred with your ... flow" Email is Sent to System Administrators

When a Salesforce Survey response is submitted, an error email similar to the following may be sent to the Salesforce administrator:
Subject: An error occurred with your "(Survey Name)" flow
Body: An error has occurred while processing your request. The salesforce.com support team has been notified of the problem. ... Error ID: xxxxxxxxxx-xxxx (-1402570930)

Cause

This error is expected system behavior. It occurs when a respondent attempts to submit a response again to a completed survey invitation that is not set to anonymous.
For example, this notification is triggered when the system detects a duplicate submission attempt — such as when a survey respondent opens the same invitation link in multiple browser tabs, completes the survey in the first tab, and then immediately attempts to submit from the other tab.

Resolution

If this issue occurs, advise survey respondents not to perform actions such as opening the survey in multiple tabs or attempting to submit responses multiple times after completion.

Reference Information

Salesforce Surveys are designed so that, when not set to anonymous, the same user cannot submit multiple responses. For related information, refer to the Additional Resources section below.