Hello,
Before I proceed with more information, test the demo on another device and if the problem persists then you can read the rest of my bid :) . But if the problem doesn't happen on a different hardware then it is a hardware issue. I have run into similar problems a lot.
About me: I am Unity developer wit 7+ years of experience and I currently specialize in VR and AR (Oculus Rift, HTC Vive, AFrame, Google Cardboard, Google Daydream, Gear VR, ARKit, ARCore, Vuforia, etc.).
I work in a team of 5 developers and a few artists (2D and 3D with their numbers fluctuating based on our current needs).
Sadly I can't send you any sample stuff or portfolio because most of our works are covered by NDA as they are outsourced to us from California (We would like to honor the contract).
However, if we do a video chat I can give you a tour around our office and show you a few things that we have done, but I can't send anything over.
Please do let me know how your test goes and we can hopefully talk further about your issue.
Hope to hear from you soon and good luck with your project.
Regards.