Concurrent employments, global assignments, rehires and contingent worker to employee conversions (among others) always trigger the creation of a new user record in the LMS. If the employee had already completed or started courses that should be transferred to the new user record, administrators are responsible for merging both records. This manual process is risky and may overwhelm administrators of large companies.
Suggestion on how the issue can be addressed:
Replacing the User ID by the Person ID External as the STUD_ID field in the connector file (this is already possible via Integration Center) and also use it to authenticate the LMS' SSO may resolve this, as new users wouldn't be created by the events above and employees would be able to access their initial LMS record no matter their current User ID in BizX. Creating an option in the LMS' System Configuration or in Provisioning to allow customers to decide which field (User ID or Person ID External) they want to use would be ideal, as some companies may prefer that new users are created anyway.