Sorry it hadn't loaded when I sent that message.
Unfortunately our issue with Unbounce is how Unbounce loads file downloads.
Unbounce allows file downloads by redirecting to a new url when the user completes the required form; but specifically, its a redirect to a new url on the original tab. When the redirect occurs we lose any tracking that is running on the current tab.
To get past this, we inserted a time delay when the user clicked "Download" in order to give our tracking time to execute before the redirect happened. In some cases the time delay was more than enough and in others it was not enough - hence why we would have data inaccuracy. We didn't want to increase the delay timeout because that would seriously affect UX, and we would likely get users resubmitting the form and possibly record duplicate events of that download.
Hope this makes sense. We are looking into whether we can redirect to the "download" url in a new, separate tab, this should allow the tracking on the original tab to execute uninterrupted and give us accuracy.