Errors in submission form (incomplete values)

We are currently experiencing errors with our submission form and are unsure why this happens.

When clicking submit, an error comes up (as in the screenshot attached). We have ensured that documents are attached in the required fields.

We have tried this from different laptops and it happens almost every time, however sometimes it goes through. I have not found any logic between when it is submitted and when it is not. 

I hope you can help solving this issue.

Thank you in advance.

Jotform replied this:

I have replicated your issue by submitting your form several times. However, in my cloned form, the error does not occur so it is isolated to your form. I have escalated this to our development team for further checking. We will inform you once this is fixed.

They have not fixed it yet, does anyone know how to do this?

This is a duplicate thread. We will update you on your other thread: https://www.jotform.com/answers/839875 

If you have any followup questions regarding this issue, please post your reply on that thread.