The first thing to check is to make sure that your 'Order' entity is properly mapped in your database, and there are no existing entries with duplicate ID's that might clash with each other.
The issue might also be because your 'order_id' is not being generated correctly or is not unique resulting in the duplicate error. In your 'Order' entity, you have specified '@GeneratedValue(strategy = GenerationType.UUID)' for your 'orderId' field, but it looks like it might not be working as expected.
To create proper unique 'UUIDs' for your 'order_id' you can update the '@GeneratedValue' annotation for 'orderId' using -
@Id
@GeneratedValue(generator = "uuid2")
@GenericGenerator(name = "uuid2", strategy = "uuid2")
private String orderId;