It is theorized the eight corner cubes will be less stable as they are only "balanced" by squarely touching three other cubes. These three influencing polar states of the Corner Cube Retro-Reflectors will be unstable enough to initiate vortex motions in each corner cube. Keeping in mind each of these 27 cubes contains a centralized "particle" of matter. The stabilities and instabilities of the cubes would be the same for the contained particles.
See Also
6.6 - Cube Corner Retroreflectors
6.14.1 - Mirror Cube
10.08 - Corner Vortices
Corner Cube Retro-Reflectors
Corner cube retroreflectors
Figure 2.1.5 - Russells Rings forming Spheres from Three Pairs of Reflecting Mirrors
Figure 6.11 - Cube Corner Reflectors Dissipating and Concentrating
Mirrors and Lens of Cosmic Cinema
Part 06 - Formation of Cubes