open the attached project
Note that the "blade instance" object has a scale of -1 in the X axis to flip the model
render to picture viewer
The spinning blade will blur correctly
Set the "blade instance" scale from -1 to 1 to reset the model back to its real shape
render to picture viewer
bug: there is no motion blur
There is a second odd / related behaviour. If you drag the "blades" object from being a child of "group 1" and move it to "group 2", then the motion blur will work again.
My guess is that octane is looking at the "group 2 object" being instanced, sees the only thing inside is a null, and doesnt then check the children to see if there is any moving geometry it should consider. The fact that a -1 scale on the model fixes it though I cannot explain.
octane 2023.1.2 r5
c4d 2024.2.0
win 11
gf 3090