why do shapes vanish when on a box

when I place a shape on a box it vanishes completely now and then when rotating

I know there is z-fighting which can be seen when a rectangle is on a rectangle but wouldn't expect it to vanish completely. Tried to do grouping to fix it but doesn't seem to make a difference.

see simple demo I created here, thanks.

https://codepen.io/coder787/pen/MWJbJQo

Start with the linked CodePen demo and reproduce the disappearing shape while rotating overlapping shapes. Trace the rendering behavior for shapes placed on boxes, then verify that the shape remains visible during rotation without introducing the reported z-fighting issue.

Written by the indexing model from the issue text.