The initial shape consists of the set [0,0.5] x [0,1] x [0,1] with the addition of the set [-.5,1] x [0,0.25] x [0,1] (the second coordinate is height, the third coordinate is depth).

A degenerate breaking face is artificially introduced at x = 0.5 into the front and back faces; it will widen during the evolution!

The subsequent evolution tends to widen this strip, signalling that this evolution is energetically better than the one without breakings. This is the situation at time 0.005:

And then at times 0.01, 0.015, 0.02, 0.025: