I am using SharePoint 2013 and Nintex 2013.

I had a Nintex form with an unconnected hyperlink field. Some users went into the form and they have updated that field with URLs. That's fine.

I later decided I wanted to create a column in my list to capture that hyperlink value (because I wanted to export the data to Excel). So in my list I created a new 'Hyperlink or Picture' column called ScheduleLink.

I then went to the Nintex form and connected the previously unconnected hyperlink field to that new column called ScheduleLink.

The only problem is, in the records where there were URLs, now users are not able to have a blank value. If the users decided to delete the previous URLs, the value will reappear!

This is what happens: they delete the URLs and it looks like it disappears. Then they click Save. It looks like the value is gone, but if the user opens the form again, the values magically are still there! The values are gone from the list view, but they are still there in the form. It seems like SharePoint considers the existing value that was in place when the field was connected, to be the default value when blank.  It seems like a bug to me.

In other words: there are URL values in an unconnected field. I later connect that field to a column. But now strangely, SharePoint doesn't allow that column to be blank. If the user tries to delete the URL in that field, it looks like it's gone, but the value reappears when the form is reopened.

Where does SharePoint store the values for unconnected fields?

Thanks