When a user is traveling to another instance, particularly one that is open and joinable, the join button remains visible during mid-travel. However, even when the prompt to join them appears, it is not possible to join. A tooltip will display, stating: "Unable to join. User is in a private world." The action will update their state though if they arrive in their destination instance during.

The correct behavior should be that the Request Invite button only updates to the Join User button once the user's state properly indicates they are in a open and joinable instance.