I found a workaround. I put the form onto a blank page, and have the page content load within the popup using an object tag.
I have this same problem with a different popup plugin (boxzilla).
I am looking for a solution, but for now it’s a big problem. I have conditional fields in my popup that stop working when the popup is closed and reopened, so some of the fields remain hidden regardless of how the form is filled.
Does anyone have a workaround? Have you found a solution?