You've set up your webform, it's live, people are beginning to submit responses, you go to check the results, and instead of one entry per person, you see three. Or five. Or eight. What is going on here?

It took some investigation, but it appears it's possible that a few different combinations of settings in a webform can trigger a specific line of render code to repeat itself. When this happens, the triggered code creates multiple entries in your Results screen.

Inline Confirmation is enabled

It's possible that the manner you've chosen to notify the person submitting your form that the process has completed successfully may be at fault. Something in the page refresh triggers the above-mentioned render code repeatedly. You can avoid this by taking the following steps:

1. Navigate to Manage » Structure » Webforms or go directly to the page with your webform attached and use its contextual menu to Edit the form settings.
2. In your form, click on the Settings » Confirmation submenu link.
3. Under the Confirmation Type label, change your setting from Inline to Page.
4. Scroll to the bottom of the screen and click the Save button to finish.

Multiple Webforms on the same page

The presence of two or more webforms on the same page may cause multiple entries. Verify that you haven't added the same webform as a block on a page with the full webform node. If you have multiple webform blocks on the page, consider testing if reducing them or restructuring how people access the webforms resolves the problem. Example: instead of having the forms all on one page, can you link to each one on their own page instead? 

As needed, this article will be updated as more triggers and their solutions are identified.