Hibernate throwing error in One-to-one relationship

Question

I am trying to implement a one-to-one mapping and below is the entities involved:

UserID which acts as composite primary key:

@Embeddable
public class UserID  implements Serializable {
    private static final long serialVersionUID = 1L;
    private int ssnID;
    // getters and setters...
}

Vehicle Entity:

@Entity
public class Vehicle {
    @Id
    private int vehicleID;
    private String description;
    // getters and  setters..
}

UserInfo entity which has UserID as composite primary key and having one-to-one relationship with Vehicle Entity:

@Entity
public class UserInfo {
    @EmbeddedId
    UserID userID; // Object which acts as a primary key (composite primary key)
    private String full_name;
    @OneToOne
    @JoinColumn(name="VEHICLE_ID")
    Vehicle veh;
    // Getters and Setters...
}

UserInfo is the owning-side entity as it has the FK (using @JoinColumn) and has UserID as composite primary key.

When I save the UserInfo object, the below are the sql logs of the hibernate:

Hibernate: drop table UserInfo if exists

Hibernate: drop table Vehicle if exists

Hibernate: create table UserInfo (ssnID integer not null, full_name varchar(255), VEHICLE_ID integer, primary key (ssnID))

Hibernate: create table Vehicle (vehicleID integer not null, description varchar(255), primary key (vehicleID))

Hibernate: alter table UserInfo add constraint FK9nx05ha53jhcue5rwks77x0mv foreign key (VEHICLE_ID) references Vehicle

After this, it throws the exception:

ERROR: Referential integrity constraint violation: "FK9NX05HA53JHCUE5RWKS77X0MV: PUBLIC.USERINFO FOREIGN KEY(VEHICLE_ID) REFERENCES PUBLIC.VEHICLE(VEHICLEID) (100)"; SQL statement:
update UserInfo set full_name=?, VEHICLE_ID=? where ssnID=? [23506-190]


Caused by: org.h2.jdbc.JdbcSQLException: Referential integrity constraint violation: "FK9NX05HA53JHCUE5RWKS77X0MV: PUBLIC.USERINFO FOREIGN KEY(VEHICLE_ID) 
REFERENCES PUBLIC.VEHICLE(VEHICLEID) (100)"; SQL statement:
update UserInfo set full_name=?, VEHICLE_ID=? where ssnID=? [23506-190]

I am not able to understand why this is throwing the exception; I am not inserting any duplicate values.

Is there any issues in my mapping using @OneToOne or @JoinColumn?

Can anyone help me understand this?

EDIT:

I have created a helper class which does the actual saving, part of the snippet is:

public void saveUser(UserInfo userInfo) {
    Session session = null;
    session = sf.openSession();
    session.beginTransaction();
    session.save(userInfo);
    session.getTransaction().commit();
    session.close();
}

So, from main() I call this helper method, and save the Entity UserInfo (which has the other entity Vehicle set).

Please note I am not saving the Vehicle entity, does it need to be saved explicit?