Animating a component hides the component inside it. How do I fix this?

[dark spindle]

Hi, I'm trying to animate a part of my model, which has a large cube with a small cube inside it.

I've animated the large cube, but in doing so, the small inner cube is not always visible.

How can I fix this so that the small inner cube is always visible?

(The larger cube is highly transparent, Opacity 20 out of 255)

[candid elk]

The opacity is the issue - Blockbench has trouble rendering that