Wrong variant (smallest or default) added to cart on IE and sometimes Chrome / Prestige theme

[moorka]

Our customers report that when they try to order an out of stock size, they do not see it is out of stock and he smallest size is added to cart instead. They are angry about having received the wrong size and we are unable to prevent this. I am not able to replicate this issue in any browser on Mac, but my colleague on PC could replicate on IE and in some cases on Chrome.

Looking through other similar subjects I see that an app is often causing this, but we have no exotic apps - only Facebook, Google.

On our previous theme we had a similar problem where the add to cart button was not updated fast enough, so the developer pre-blocked it until the correct variation was passed to it. Is this a common issue and is there a known solution for Prestige? I have written to their support, too.