Using username restriction, users may respond twice (but no more)

Did they complete their first survey? Unless they click on finish button on the last page, their survey will be in progress and they can make changes to it. 

Yes, they did.  This is a one-page survey with two text questions.  The survey is reached via a single-survey menu item.  After answering the survey once and clicking Finish, that answer displays properly on the back end. 

But they can then click the menu item a second time.  That time, their previous answer is pre-filled in the text fields.  If they change it and click Finish again, the survey completes and the new answer replaces the old one in the back end. 

The third time they click the menu item, it properly states that they already completed the survey.  This behavior is consistent every time we try it. 

Thanks again, Maverick.

I am able to reproduce this issue.

In one page survey, the user response is created when the answers are submitted. Since there is no other page, the response is immediately finalized. Since there is only milliseconds gap between the creation and finalization of the response, the response is not recognized as finalized. To fix this issue, I added a one second to the completed date in the response table so that the calculation will be done properly.

Please update v5.5.7 to fix the issue.