Reply To: Display of background header image is not ok on iOS / iPhone

Dear Julien,
Such issues are common for the iOS devices as Safari browser still does not support background-attachment: fixed; property. But it should not appear on the Android devices.
But you can add the following code in Additional CSS for removing the blurry image from all mobile devices.
Appearance > Customize > Additional CSS

@media(max-width:767px){
    .inner-main-title{
       background-attachment: scroll !important;
   }
}

(Note: it will change in all mobile devices)

Best Regards!