every submission seems to generate "Your submission appears to be a duplicate."

Question

Everytime I post a response to a question, I get the following error message:

Your submission appears to be a duplicate.

Any ideas what might be wrong with my setup?

Comments

That is very odd. Can you post a link? Any non-core plugins?

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I just encountered with the same issue while developing plugin and using event module to insert value to custom table.

Answer 1

It happens if there's some PHP error generated by the Ajax response Javascript. This causes the Ajax not to respond properly, even though it submitted the content. In turn this causes the page to retry using non-Ajax submission, but since the content was already submitted, it is not a duplicate. Check your server's error_log for the solution.