Our users do this all the time for whatever reason.  What the user will do is go into the one they completed and then do a change session at the top right to choose another session/event they would like to attend.  This is how we do it.  Not sure if there’s another directive.

Typically users cannot take more than 1 session per course. An admin can enrol them in multiple sessions but users cannot. 

We use archiving to archive the session/completed course and thus allow the user to reenrol into a new session on the same course.

If you unenroll users from a session to be enrolled dint another, the data of the first session disappears from your reports since tracking is related to enrolments. Only archiving will commit the record to the user’s transcript permanently.

Thank you so much for your response.  You are totally correct - the tracking data disappears.  I have to do metrics on a weekly basis to capture this.  I’m reviewing more on the archiving process.