Api Method InsertRecords on Quotes Module get Error 4500: Problem occured while processing the request

Hi

I'm trying to insert a new Quote record using the insertrecord method as described on
https://www.zoho.com/crm/help/api/insertrecords.html#Quotes

url: https://crm.zoho.com/crm/private/xml/Quotes/insertRecords
?authtoken=AUTHCODEHERE&scope=crmapi&newFormat=1&duplicateCheck=2&version=4&wfTrigger=false

XMLDATA as POST is:

<Quotes>

<row no="1">
<FL val="Subject">prueba techdev</FL>
<FL val="Due Date">2015-08-08</FL>
<FL val="Sub Total">100.0</FL>
<FL val="Tax">0.0</FL>
<FL val="Adjustment">0.0</FL>
<FL val="Grand Total">100.0</FL>

<FL val="Terms and Conditions">Prueba TechDev</FL>
<FL val="Description">Prueba Integracion TechDev</FL>
<FL val="Product Details">
<product no="1">
<FL val="Product Id">xxxxxxxxxxxxxxx</FL> < The ID of the product already exist on zoho and is a valid id
<FL val="Unit Price">100.0</FL>
<FL val="Quantity">1.0</FL>
<FL val="Total">100.0</FL>
<FL val="Discount">0.0</FL>
<FL val="Total After Discount">100.0</FL>
<FL val="List Price">100.0</FL>
<FL val="Net Total">100.0</FL>
</product>
</FL>

</row>
</Quotes>

But the response is:

<?xml version="1.0" encoding="UTF-8" ?>
<response uri="/crm/private/xml/Quotes/insertRecords">
<error>
<code>4500</code>
<message>Problem occured while processing the request</message>
</error>
</response>

So according to:

https://www.zoho.com/crm/help/api/error-messages.html

This mean

4500 Internal server error while processing this request

So I wonder what is wrong

Please note that this error only occur on Quotes Module so far, I have succesfully inserted records on other modules.

I have tried almost every combination of fields, including

QUOTE LEVEL FIELDS:
==================
Subject
ACCOUNTID
Account Name
SMOWNERID
Quote Owner
SMCREATORID
Created By
MODIFIEDBY
Modified By
Created Time
Modified Time
Due Date
Sub Total
Tax
Adjustment
Grand Total
Discount
Terms and Conditions
Description

PRUDUCT LEVEL FIELDS
===================
Product Id
Product Name
Unit Price
Quantity
Total
Discount
Total After Discount
List Price
Net Total
Tax
Line Tax
Product Description

API user is root on an enterprise account.

Any suggestions?

Another little glitch GetRecordsByID method on a quote record dont retrieve the due date field

PD: references to this error are more than 5 years old, and don't apply to current API version used.