A user may see a different site branding after they login to our system from your site. This happens when a user is owned by one publication and attempting to post to another. In this case, a user starts their submission at one site and, during the course of the posting, they are asked for an account email. If their email is in our system then they will need to login. At that point we will recognize them as belonging to another publication.
In this case, the publication calendar where they started their submission will be the site to which we will try to send the event. If at any point during the submission the users opts to login before they are prompted to by the submission process, then their submission may be sent to the owning publication. More info about how our system works in this way is here: How does Evvnt work?
If this causes an issue for any user, one solution is to move the customer if they would like to be primarily posting to a different site. If not, then if they would like to post to another publication they would need to follow these guidelines: Can I post to a different publication for my events?