Displacement disappearing in fisheye cam

[sg_artist]

Hi all,

I'm using a fisheye cam in Arnold to render a large scene for my VR porject.
I apply several triplanar maps to displacement node to build the environment,
and it works totally fine while rendering in perspective mode.
However, once I switch to fisheye mode with 180° FOV,
the displacement gets disappearing if one object is close to the camera and near the boundary of the picture.
(unfortunately I can't provide the final render. This is how it looks like:

I try different camera settings, and this problem only happens when FOV is larger than 150°.
Also I try rendering another object with a simple 2D displacement map,
it has no problem in 180° FOV fisheye cam.

The below is my camera, triplanar map setting and arnold version info:

Does anyone meet this situation before?
It would be appreciated if there is any tip or advice, thanks!