Intermittent Issues form not submitting

Every once in a while I have a rash of people who cannot successfully complete my form.  They will complete all the information, hit submit and it will glitch, coming up with a blank screen.  Some believe it has submitted correctly but I (and they) do not receive it.  I have had another rush of these in the last few days and have made NO changes to the website or form.  It is imbedded in my website but I've also sent the direct jotform.com link without success.  I will receive one or two, but the majority will not be received.  Please help me troubleshoot this issue as it is a huge inconvenience to my clients.
Thank you.

We do apologize for the inconvenience.

I have checked your webpage and it seems you have embedded your form in an Iframe and should be working correctly.

May we know if your form user's receive an error message when submitting the form?

May we know the web browser they're using to fill the form?

I have checked your mail logs and all notification emails are sent.

You may suggest disabling any pop-up blockers in the web browser when they're filling the form.

If possible, can we have the form user's console reports when the issue is replicated. Here is a guide:How-to-get-a-console-report-from-most-common-browsers

I have cleared your form cache.

Thanks for your quick response.  Every time I test it, it works fine.  But I've had at least 3 people fail and don't have a lot of feedback from them.  Once person shared: 

Tried 2 more times and when it tries to send just goes to the black home screen.  I tried on my iPhone and on my iPad.

One other client was likely on an iPhone, so I'm worried that may be related to the issue?

I don't always know when someone will complete it, so it's hard for them to capture any reports as I find out later it never went through.  Most people don't know if it went through or not.

I have tested a cloned version of your form but I can't replicate the issue.

Your form is using the default thank you page when the form is submitted.

Can we test a submission using your form?

Looking forward for your response.

Yes, testing is fine.  I can't replicate the issue either.

I was able to replicate the issue using my iPhone. It seems your web page is showing a captcha field after the form is submitted. However, your form user's cannot view the captcha field as they need to use the auto scroll(arrow in the right) in your web page.

Here is a screen cast:

This usually happens when there is conflict between your web page and the embedded form.

Can you please try re-embedding your form using Iframe without the script code?

Please give it a try and let us know if you have made the changes so that we can test it out.

If I copy & paste the iframe section you have highlighted into the code box (deleting everything after as noted by your graphic above) it only shows the form header on the website, no actual form??

I re-pasted the entire code again, can you re-test on iphone?

I was able to submit the embedded form. It seems your form is working correctly now.

Kindly check your notification email and let us know if the issue still remains.