Hello,
New poster here 
I have a scene where the door of a plane is flapping very fast in the wind. The problem I’m having is the motion blur seems to only be calculating every 2 frames in render, I see the substeps (multiple geometry samples) being calculated in maya when I do a preview render but the door sticks, then it moves after 2 frames, sticks, then it moves again. Some of the steps I’ve taken to try to correct this is baking the anim on the door so there is a key every frame. I baked out the door anim as an alembic with 4 substeps, I matched the geometry samples to those 4 substeps. It doesn’t seem like anything I do makes a difference, there are still stalled frames. Has anyone had this problem? There must be something that I’m missing. I’m using Maya 2016 and Vray 3.1. Thanks!