Responses showing up days after submission

I created a form a couple months ago and have gotten steady responses.  I receive most of the notification emails within 5 minutes of submission but every once in a while I will get a notification email for a form that was submitted several days ago.  I added a new question recently and the delayed responses don't have answers to them so i can tell they are from the previous version.  I look in the submissions page of the form and the timestamp for submission shows the current time so its like the form is filled out but not delivered until days later.  Any idea how this could happen?  Is there something that can be don't to ensure consistency?  is it a user error?  Let me know if you have any questions.  

In order to avoid email delivery issues, we would recommend you to setup your own SMTP sender. Sending via SMTP sends directly from that address taking our servers out of equation. Here is the guide:

https://www.jotform.com/help/244-How-to-Setup-SMTP-for-a-Form

If your new question does not appear in the e-mail notifications, please try to delete the notifiacation and then add it again on the form.

Please try these simple fixes and let us know, if they help.

We will wait for your response.