Tried to look up for older post of me, about same subject: years ago, same issue.

When I use a stock photo, before uploading I purchase the image. When I go to preview the process will take hours. The solution I found is to save the file after the purchase, and important, close the project and reboot. When I than replace the - standard m - file with the local stored file, and preview and upload project, it is a matter of minutes.

So Eric, a FYI. Found a way to work around the issue, but it is weard that going straight forward there is a wall ready for the user, and that if you want to not knock your nose to the wall of rendering time, the credo is: find a way.....

The only thing that is left, that all pages needs a new upload. While there is only 1 or 2 pages changed. But hey, who cares. Altough I see it as a risk when more gets uploaded than that is changed.