Problem solved: when studying in wordlist mode Popup Chinese suggests words for review depending on your SRS schedule. So if you only have two or three words to study, it will only give you two or three rather than the number you might have requested on your settings page.
This led to a problem (now fixed) in situations where people had fewer words to review than their default requested review size. In these cases the system would start at the default size, and then cut to the "victory screen" once everything was reviewed. This has been fixed by making the system properly identify the number of words left to review when studying from SRS vocab.
There was also a minor issue that was resulting in the popup review not loading for a subset of users that has been fixed as well.