AN UPDATE:
We are checking with the maker of the PDF Flipbook program on this. In the meantime, could those of you having the problem do some troubleshooting for us? Go back a couple of issues and see if you have the problem with runs 322 or 325 - back in that time period.
We are trying to determine if there is a problem with the PDF Flipbook program or whether we have a problem with the PDF file used to make the Flipbook for the current issue.
In the meantime, the solution is to download the issue, instead of reading it online. It will download completely.