Very strange behaviour when reordering products inside a category

[Antakarana]

Hi

Recently we have noticed a very strange behaviour on a Prestashop site at the time of reordering products in a category. The shop is using PS 1.7.5.2 with the  warehouse 4.2.1 template. The following is a description of the correct behaviour:

When a backoffice user wants to reorder a product position (or serveral product positions) inside a category, he saved the new positions by pressing the following button ("Guardar y actualizar" - "Save and update"):

After that he sees that the button changes to this one ("Pedir de nuevo" - "Ask again"), by pressing it the user is able to reordering the products again.

Until that point everything is OK....

The problem that the user is only able of doing this procedur once, because the second time that he tries to reorder the products, the "Pedir de nuevo " button (Ask again) doesn't appears... instead it shows the "Guardar y actualizar" button (Save and update).

First we thought that it maybe a browser cookies-cache issue so we asked him to clear the browser cache-cookies by using CCleaner. He did, and it worked fine.....however it just worked once. 😅

When he tried again by clearing cache and cookies it doesn't work anymore. Also he tries to do it from different browsers and PC with no luck.

So I tried to do the same procedure from my house and it worked without any issue. No matter how many times I try to reorder and save the new positions, it always worked (like it should be). At that point I thought that maybe the user was doing something wrong. 

So I asked him to open a TeamViewer session and I asked him to perform the procedur to check if it was doing some mistake.

Then things turn very strange, when we realized that, if the user performs the procedur, then it doesnt work, however if I take control of the mouse (by teamviewer) and I press the "Save and update" button, then it worked perfectly....

WTF????

😦😦😦😦😦😦

So the same computer, the same browser, the same backoffice user, the same prestashop session and two different results depending on who is pressing the "Save and Update" button.....

- Me (remotely by teamviewer) --> works perfect

- the user (localy) --> doesnt work

We tried it several times with the same results so it can not be a coincidence. 

I can't explain that behaviour..... .......Do you have any idea of what is suposed to be happening??

thanks in adavance

[Antakarana]

As I expected, nobody has seen something like that before............. 😓