GearVR viewport issue

Hi,

Working on a VR app for GearVR, we realized that our reticle seemed to be a little shiffted on the right.
I tried to watch the phone screen outside the Gear and i realized that (have a look to the screenshot).

The screenshot was taken on a galaxy s7 edge, we have the same thing on a standard galaxy s7.

Is this a Unity bug (i'm on 5.4) ?
Does anybody have a tip to correct that ?

Thanks