Issue with [_url] tag and pop-up

I’m having an issue where the [_url] tag is generating the incorrect URL upon submission. Regardless of the page the form was submitted on, the [_url] tag will generate the first URL the user landed on. This particular form is within a pop-up (via plugin “Popup Maker”). I’m not sure if that has anything to do with the issue, but I suspect it might. However, this didn’t use to be an issue and this form has always been within a pop-up.