Slow Preparing Geometry

[BigAl3D]

I'm curious if there is a typical reason why a scene can spend a lot of time Preparing Geometry before actual rendering begins? The image below is my scene. A grid of cars in a Mograph Cloner set to Render Instances. These cars are relatively hi-res models.

Size of texture files?
Calculating displacement?

I'm at a loss to narrow it down. This is one frame of an animation where the vehicles flip up out of the floor. It will sit there for 8 minutes at Preparing Geometry and then as little as 4 min. to actually render.

Mac OS 13.6.7 Ventura
Corona 12 Build timestamp • Jul  1 2024 11:08:36

[BigAl3D]

Just collected the project and checked out all the texture file. I did find one large file, almost 300 MB, that did not need to be that size. I resized and Photoshop and replaced. Still taking 9 mi. to prepare geometry. I'm sure there are many displacement maps on these cars. Is there a way to remove displace at render time or any other way?

[BigAl3D]

Turned of most displacement in the materials and changed the Displacement setting to World --- No difference at all.

Switched to Path Tracing. Lighting is Physical Sky and Sun object --- Cut the render time in half.  ***Edit*** I also turned OFF motion blur. I think that's the culprit. I think the default settings of 4 and 1 segments. Sigh.