IntegrityError: (1062, "Duplicate entry '25503' for key 'user_id'")

[sentry]

What's the source of this error?

Sentry Issue: OPENEDX-RESIDENTIAL-48D

LastSeenCoursewareTimezone.DoesNotExist: LastSeenCoursewareTimezone matching query does not exist.
  File "django/db/models/query.py", line 581, in get_or_create
    return self.get(**kwargs), False
  File "django/db/models/query.py", line 435, in get
    raise self.model.DoesNotExist(

IntegrityError: (1062, "Duplicate entry '25503' for key 'user_id'")
(1 additional frame(s) were not displayed)
...
  File "django/db/backends/mysql/base.py", line 73, in execute
    return self.cursor.execute(query, args)
  File "MySQLdb/cursors.py", line 206, in execute
    res = self._query(query)
  File "MySQLdb/cursors.py", line 320, in _query
    self._do_get_result(db)
  File "MySQLdb/cursors.py", line 145, in _do_get_result
    self._result = result = self._get_result()
  File "MySQLdb/cursors.py", line 352, in _get_result
    return self._get_db().store_result()

IntegrityError: (1062, "Duplicate entry '25503' for key 'user_id'")
(29 additional frame(s) were not displayed)
...
  File "django/db/backends/mysql/base.py", line 73, in execute
    return self.cursor.execute(query, args)
  File "MySQLdb/cursors.py", line 206, in execute
    res = self._query(query)
  File "MySQLdb/cursors.py", line 320, in _query
    self._do_get_result(db)
  File "MySQLdb/cursors.py", line 145, in _do_get_result
    self._result = result = self._get_result()
  File "MySQLdb/cursors.py", line 352, in _get_result
    return self._get_db().store_result()