I made a simple VR app for android using Google VR plugin installed with [this][1] method, except I copied from 4.20 version. While the app works on android, left image is visibly more distorted. It looks zoomed in for some reason. You can tell by how the shadow looks bigger in the left image and the jacket is stretched.
When playing from the editor, is looks fine. The distortion difference appears only while working on android.
I’m getting the same issue on 4.25 on a Samsung Galaxy S8.
I set it to support hardware configurations for Cardboard only to at least get the right eye working, adding Daydream 3:3DoF to the hardware configurations made the app black, constantly crash and sometimes artifact the entire screen with green pulsing speckled lines, looks like GPU memory.
I thought android deployment alone was a headache, this seems so much worse 
I’m facing the same issue on my Xiaomi MI6 when deploying Google Cardboard VR project (from editor it works ok). What helped me, was to enable Mobile HDR in Rendering options. I compared default VR FPS project settings (which works ok on my device) with my own one and Mobile HDR was among only 2 or 3 differences. Of course this is more a workaround and not a solution as it is adviced to disable this option for mobile VR projects. Still maybe this will point someone to a correct root of the problem.
It could be caused by wrong Cardboard viewer settings. They are used to setup the cameras, the projection matrix and the distortion mesh. On Android they’re globally cached and restoring the default values is hard. But you could simply scan the QR code for the original V1 (or V2) Cardboard and check if it fixes the problem. You can find such QR codes here https://homido.com/en/les-principaux-qr-codes-pour-casques-vr-passifs/.
If still developing for Google Cardboard, you could also be interested in our plugin “Cardboard VR”, that integrates the new Google Cardboard SDK in UE4, for both iOS and Android: https://www.unrealengine.com/marketplace/cardboard-vr .
