How to reproduce:

1. In the app, go to a course, go to participants and open a user profile. Check that you see "Send message".
2. Without leaving the user profile, click the "More tab" (3 dots) and click to open your own profile. You'll briefly see the "Send message" button, but it should disappear quickly (this could be improved too, probably related to the issue).
3. Without leaving the view, click the courses tab so you're back to the other user profile. Check that you no longer see the "Send message" button (it should still appear).

The same happens the opposite way, you can make that button appear in your own profile. I guess the list of addons to display is unique to all users when it shouldn't be anymore.