Hi Gustavo..
Yes.. we tried with a couple of the basic themes, and still had the same results. I turned off all other plugins as well just to be certain. Still happens.
Interesting that it only seems to happen on the 5 and 5s – and not consistently. It happens on some of them, but not all of them. We did an exhaustive search through the settings of each… and could not find anything odd or different between them. I even tried using an iPod and it worked fine on that as well.
So I’m thinking that there must be something about the model that was being used that causes it. Since we cannot replicate this anywhere else – that’s all that I can think that’s left.