Hello,
this is a known issue and is in our to do list. A workaround for this would be to use a Physical camera and then override the current camera type. To do this make sure you disable the orthographic option from the camera and then while the camera is still selected add the following attributes from the Attributes Editor to the camera shape node:
Attributes > V-Ray > Physical Camera
Attributes > V-Ray > Camera Settings
In the Camera settings extra attributes chose the camera type to be “Orthogonal” and then chose the desired FOV if needed.
You can find more info here: Chaos Docs
Thanks for your feedback and let me know if this works for you.