"Duplicate submission" error

Hi there

I don’t know if there’ll be an easy answer to this. We have a feedback web form that is set up to allow multiple submissions from the same users (they click on a part of the site, get the feedback box, submit, then repeat on other parts of the site).

1 user (out of about 75) has reported an error saying “Duplicate submission” and it seems to not be allowing them to submit more responses. They’ve successfully submitted over 20 responses, and we’ve got others who have submitted 40+ without issues, so it seems localised to them.

Unfortunately they’re an external user and the project this was linked to has now ended, so we don’t have any way to get more information than the error itself in the screenshot below. I’ve tried to recreate the error but haven’t managed to - I can submit repeated responses on the same form, even with identical text, and they all go through fine as expected.

I’m hoping someone might be able to give me some pointers as what behaviour should trigger this “Duplicate submission” error, so that I can try and plan for it in future and hopefully avoid it reoccurring. My guess is there’s an ID in the background that isn’t clearing out for this one person, so perhaps getting them to clear their browser cache might resolve it in future. Since we want duplicate submissions in this case, is there a way to ensure the form is fully reset each time so that it doesn’t give this error?