Override Default Pawn's position and orientation makes the Oculus IPD to 0

Hello All,

We are doing a VR experiment using Oculus and Unreal. In this experiment, we just use Oculus as a display device and disable Oculus’s positioning and orientation like the following:
And we use the Vicon to provide the positioning and the orientation for the default pawn, the blueprint looks like the following:

After doing this, we realize that the ipd of oculus is set to a very small number (close to 0, left and right eyes see almost identical image from the Oculus Rift). We search solution for days on the internet but found nothing. Does anyone one knows how to solve this?