Modal popup changes behavior on click?

Hello!
I love this plugin and everything seems to work well except for this weird instance with the modal popup. On the first click, the modal popup appears in the top right corner with half of it hidden on the right side of the screen. If you scroll over, the modal will move so that half is still hidden. It does this indefinitely.
But if you click the modal once, close it, then open it again, it appears centered in the screen and will scroll with you beautifully.

I’m not sure why this popup changes it’s positioning from the first to second click. It’s a 100% reliable bug to create too, but I have no console errors. I tried hunting for the lines in the plugin file where this issue might be triggering but even de-minified the code is really, really cryptic.

From what I can tell, the style output difference between click one and click two are that click two has “display:block;” applied to the “mega-model-popup” class, but click one does not add this style.

Any chance you can help with this?

Thank you!