This looks like coincident surfaces.You should scale down the lenses (or up the housing) the tiniest bit. Also move lenses tiniest bit apart if they have coincident surfaces.
With the diameter of the lenses scaled to 0.999 and moved some of the lenses by 0.001 I get this:
No, it is up to the creator to ensure (visible) surfaces do not end up in the same location. From two surfaces the render engine will not be able to know which one to sample. This causes ‘z-fighting’.
Here a smaller, green box inside a white, bigger box, with one side in the same location. Sometimes the white box wins, sometimes the green box: