Understanding odd results when paginating double outerjoins - flask-sqlalchemy

Question

I'm working with Flask and SQLAlchemy and I stumble on behavior I do not understand. When I build a query with .outerjoin() and .paginate() it all works well until today when I created a query with double outerjoin related from one another like on the simplified example code bellow (db is reference to SQLAlchemy). Class First has one-to-many relation with Second and Second is one-to-one with Third.
For testing purpose I have prepared three search queries. First two search_1 and search_2 works well all the time. But search_3 works only until there are two Second records related to the same First record. When there is more than one Second related to First then query returns mostly lower number of records (but not as low as when using .join instead of .outerjoin) and in some cases even higher then the number of records in First table. What's strange number of records is changing even when using different sorting order (always by columns of First model).
class First(db.Model):
__tablename__ = 'first'
id = db.Column(db.Integer, primary_key=True)
date_create = db.Column(db.DateTime, default=datetime.utcnow)
date_update = db.Column(db.DateTime)
class Second(db.Model):
__tablename__ = 'second'
id = db.Column(db.Integer, primary_key=True)
first_id = db.Column(db.Integer, db.ForeignKey('first.id'))
third_id = db.Column(db.Integer, db.ForeignKey('third.id'))
class Third(db.Model):
__tablename__ = 'third'
id = db.Column(db.Integer, primary_key=True)
date_create = db.Column(db.DateTime, default=datetime.utcnow)
# prepare base query to reuse later
outer_base = First.query \
.outerjoin(Second, Second.first_id == First.id) \
.outerjoin(Third, Third.id == Second.third_id) \
.order_by(First.id.asc())
# works well
search_1 = First.query.order_by(First.id.asc()).paginate(1, 10, False)
# works well
search_2 = outer_base.all()
# odd as hell...
search_3 = outer_base.paginate(1, 10, False)
I just want to be able to filter First records by value from Third if there is any relation created with the use of Second table. Can anyone please explain me what am I missing? Maybe the double outerjoin can be achieved differently to work with pagination?