Url redirect generates seq=1

At the end of a pretty simple straight foward WebQuerySave agent should do an URL redirect. No problem on non-prod environment but dsiplayed 404 error by adding a seq=1 to the existing URL.

What could cause the re-direct to fail and generate the seq=1? All the hidden fields are populated correctly.

There is a javascript submitdoc function with business logic to go before submitting the form…