When someone renews their membership online without logging in it creates a new record with a new Membership. The sales order for the Membership will show on their existing record if the name and email address are the same, but the mailing address is different. The actual membership will show on the duplicate record.
This issue has been resolved in version 4.97. All sites have been updated in August 2017. If you experience this error, please chat with support to provide the exact steps that were taken.
Steps to Duplicate
Go to Web and click Manage Membership Forms
Click the drop-down next to a membership level and click the URL
Without signing in on the web form, enter a name for someone who already has a constituent record
Complete the order for one membership while using a different address than is on the existing constituent record
Search for the constituent in Altru and find that a duplicate constituent record has been created
Open the original constituent record to see that the membership didn't apply, but there is a sales order for the transaction
Open the duplicate constituent record to see that the membership did apply, but that there is no sales order on the record