Questions:

Scene moves horizontally slowly (automatically) when gyro is enabled even if there is no handset movement.

Answer:

InstaVR’s head tracking is using both gyroscope and accelerometer to have smooth movement. Since accelerometer is affected by magnetic field, sometime scene will be move horizontally slowly even if user didn’t move device.

You can resolve this issue by turning “Rich Head Tracking” option off in Package > Advanced Options > Advanced Settings > Rich Head Tracking.