Disturbance in the animation render

Hi, It’s bit hard to explain the phenomena here so I’ll post some test photos

I’m getting this type of disturbed frames time to time in this cycle render. I do have motion blur enabled. Images posted here are having around 30 samples. But I have tried with 120 Samples /Disabled composite denoiser, but still getting these at the exact frame number. Someone has any idea on why this happens?

Normal render of a different frame number

I swear some of these posts are like those “Can you spot the difference?” puzzle games!

Is it really that crazy difficult to use the Grease Pencil or even Photoshop to highlight what exactly we’re supposed to be looking for? I really don’t know what I’m looking at here, all three frames look identical to me.

Hi… Sorry about that. My problem happens around here

I think it has something to do with the motion blur.

Wow that’s really weird. It looks like the geometry is totally different. You tried with disabled motion blur and everything looks good?

How are your normals looking?

Yes I tried with disabled and reduce shutter values and the particular frames were normal. Going to try rendering whole lot back with this reduced shutter value to see how it’s going to look.
Face normals are in correct direction. But I’m pretty noobish so must have done something incorrectly at some point.

What version of Blender are you using?

if disabling stopped it from happening maybe check for random keyframes on that vehicle… I once had a crazy thing like this, turns out its actually an accidental keyframe added inbetween. If the vehicle doesnt have a keyframe, check if anything parented to it has a random keyframe.

next thing u can check is copy paste cam and the vehicle into a new scene and test out whats happening with the wiered distortion.

I’m using 2.92

I checked this. There’s no keyframe in between. But, I have had applied noise modifiers for both camera and the Vehicle.
Initially I had used default motion blur settings and I re-rendered the scene keeping the same motion blur, but with a shutter curve. And the problem was gone.