hi Christopher
Yes this seems normal - the certification completion have been archived into historic records when the window for the recertification opens .
The Certification has then expired as they haven't completed the recert on time so they have to start again from primary cert path
The users don't sound as though they are being unassigned from the audience - it is when the user is reassigned to the audience that they are returned to previous state.
Hopefully this helps if not then can you create a ticket with details of the audience setting and Certification settings and also whether the same course appears in more that one certification (this is not recommended)
regards