502 Bad Gateway error upon a form submission

I've embedded a registration form on my association's annual meeting registration page. While no one has trouble seeing the form, I've had several people tell me that when they click "submit," they get the error message "502 Bad Gateway." Their submissions have been received on the JotForm website, but they don't get a confirmation email and the submissions are not showing up in the linked Google spreadsheet. What can I do to fix this?

Thank you for contacting us.

I have made several submissions on a cloned version of your form, but I have not noticed any errors or warnings.

Are you able to reproduce the error from your side? Is there are any special instructions?

I haven't been able to reproduce the error. I found out the people who had trouble had both tried using Internet Explorer, and one of them had left the form open for about ten minutes after completing it but before clicking "submit." Could either/both of those factors have caused the issue?

Hi,

Internet explorer is notoriously buggy and we usually recommend that our users use either Google Chrome or Firefox.  It is also possible that there was an issue with their browser session timing out and information not being properly forwarded upon submission.  

When I tested a cloned version of your form, I was also able to use it without issue.  If possible, have your users try using Google Chrome and see if that fixes it.  If not, please let us know and we will be happy to look into this further.

Thank you for using JotForm!