Twitter replies occasionally not threading



We have a client has noticed that replies sent from our product occasionally do not thread correctly on twitter.

For example the client replied to this twitter post: from within our app, and when you view that post on twitter it does not show any replies.

However if you look at her reply directly here:

It does show it is connected (threaded) to the above tweet.

Here is the response we got back from twitter after the reply was posted:

<?xml version="1.0"?>
<twitter-status favorited="false" retweet="false" truncated="false" created="2015-03-30T16:44:30-0300" id="582629494822961152">

<content>@JGarciaPool pasa a CIBanco, tendr&#xE1;s tasas competitivas y ser&#xE1;n m&#xE1;s bajas si eliges abonar al desarrollo sustentable.</content>

<in-reply-to screen-name="JGarciaPool" user-id="2727854753" status-id="582596555410157568"/>

<source>&lt;a href="" rel="nofollow"&gt;Radian6 -Social Media Management&lt;/a&gt;</source>


<user id="3111632952" name="Lizzet Ortiz" screen-name="Lizz_Fer3" createdAt="2015-03-27T18:37:14-0300" description="" favourites="0" followers="1" friends="60" language="es" location="" avatar=""/>


As you can see, Twitter says it has a parent, and that parent is the correct parent post. This would indicate that it is an reply. Why then is it not showing up as an @reply on the post?