Motion Blur Sometimes Works, Sometimes Does Not

[pali_rao]

I've got a scene in Modo, and have two car wheels to which I need to add motion blur. I've followed these steps:

+ Set a keyframe on frame 0 and on frame 20 - the wheels move when scrubbing through the timeline.
+ Leave the timeline on frame 18
+ Added VRay Geo Properties to both wheels, and overridden motion blur samples to 8
+ Added VRay Physical Camera to the active camera
+ Under 'Camera Effects' click on "Camera Motion Blur' under V-Ray motion Blur extra, set shutter speed to 8
+ Under VRay Physical Camera, click on "Camera Motion Blur' under 'Sampling'
+ Set shutter speed to 8

With the Render preview in Modo, it takes literally 5 minutes+ to start rendering, and does not have any motion blur (even know I know from experience, these settings - shutter speed, number samples wheel rotation DO produce mo blur)

These happened in a previous project, and I had to untick 'Exposure' in the camera settings and then tick it again to get mo blur to work!

Please could you let me know how to get this working in Modo every time?

Many thanks!

[pali_rao]

I think that I've found the cause - for some reason in the Modo Redner options, render motion blur gets turned off somehow. I didn't even know this switch was there, but making sure it's on means all is good!