Block cracking animation appears much darker where there are coinciding planes

May relate to MC-259614.

The bug

On blocks with coplanar, coinciding faces, the cracking animation is rendered once per plane, resulting in the cracks rendering much darker than they should.

How to reproduce

1. Place a wall (all four connections, plus post)
2. Get under it
3. Start breaking it
4. Observe the cracks

Expected results

Normal cracking animation.

Actual results

It looks much darker.

Further notes

Changing the model would get rid of this issue from walls specifically, but would not eliminate it from other custom models, so code changes of some sort will be required.