Coach.MultipleObjectsReturned: get() returned more than one Coach -- it returned 7!

[sentry-io]

Sentry Issue: DJANGO-GIRLS-WEBSITE-82

Coach.MultipleObjectsReturned: get() returned more than one Coach -- it returned 7!
(8 additional frame(s) were not displayed)
...
  File "django/utils/decorators.py", line 130, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "django/contrib/admin/options.py", line 1540, in changeform_view
    return self._changeform_view(request, object_id, form_url, extra_context)
  File "django/contrib/admin/options.py", line 1561, in _changeform_view
    obj = self.get_object(request, unquote(object_id), to_field)
  File "django/contrib/admin/options.py", line 763, in get_object
    return queryset.get(**{field.name: object_id})
  File "django/db/models/query.py", line 439, in get
    raise self.model.MultipleObjectsReturned(