Product atrribute dropdown changing values after selecting product

[myhappyidea]

I have a shop with Magento 1.9.4 and Ultimo theme. We have encountered a problem with configurable products.

http://realfabrica.com/pink-victoria-camping-sneakers-99304 Here is the example because it is something wierd to explain. Non available sizes are hidden.

The first time you click on the size dropdown, we can see 26, 27, 28.... as available, but as soon as you click on any size the dropdown changes and it shows the hidden ones correctly (27,28...) as 25 and 26 are not available. So, at a first glance it is showing the wrong sizes.

It makes no sense... This happens with quite few other shoe products on the site. Has this happened to anybody?

We have the same site on a dev site and it doesnt happen so maybe its a configuration issue but we have no clue.

Thanks in advance, Ana.

[Damian Culotta]

Hi @myhappyidea,

I've tried to reproduce the error but I wassn't able. Can you point me to the right product?

[myhappyidea]

Hi Damian,

The URL is: http://realfabrica.com/victoria-camping-fucsia-ultimos-numeros-99304 

Sorry i think I copied wrong. You have to look at the dropdown  pre-size selection, select whatever size and check the dropdown again. The disabled items change to the right ones on the second round but on the first one they are incorrect.

Thanks in advance!

Ana