[API] Problem when creating a Sale Order | code 36004 > The sale order number still exists

[API] Problem when creating a Sale Order | code 36004 > The sale order number still exists

Hi, 

Few weeks ago I created a system that permits to translate other platforms Orders to Zoho Books Sale Order. Everything was find and the steps done to do this was this one:
  1. Get or Create Contact 
  2. Get or Create the order with the recently created contact.
All was perfect and I could create the orders. But few days now I have this error message when I try to create the order: code 36004 > The sale order number still exists.

Ok, so I go back to the doc to check if there is something new and I try to add the parameter " ignore_auto_number_generation": false  but it's still not working.

This is my JSON string (that was working before), I replace the sensible information with #:

{"customer_id":"#########","is_inclusive_tax":false,"line_items":[{"rate":165.83,"name":"#########","description":"
#########
","quantity":1.0,"tax_id":"428886000000526149"},{"rate":7.91,"name":"
#########
","description":"
#########
","quantity":1.0,"tax_id":"428886000000526149"},{"rate":7.26,"name":"
#########
","description":"","quantity":null,"tax_id":"428886000000526149"}],"shipping_charge":"0.0","adjustment":"0.0","sub_total":null,"total":"217.21","is_emailed":false,"ignore_auto_number_generation":false,"reference_number":"WOO-5697"}

You can verify it in a more readable version here:  http://jsonviewer.stack.hu/

Any idea about where is the problem?

Thank you in advance, any help is welcome because my sync program is down for the moment...