App steals focus from input field keyboard in Canvas Overlay

I have an app on the NReal Light where I have a simple input field in a Canvas overlay (so the input field appear on the controller). I do this because my app purpose is to take photos, so having those input fields in world space would be too distracting.
My problem is that as soon as I click on the input field, the keyboard only appear for a split second before disappearing. However, if I never remove my finger from the input field I can type in just fine on the keyboard with my other hand.
Is there a way to fix this problem and make the keyboard behave normally ?
Thanks in advance

Hi, could you please record a piece of video in the Unity and show the issue for me? Thanks in advance.