I tries to build a little deco wall with railcrafts brick walls and every time the guardian ports itself into them they breack in fitted abyselstone walls. This is wall variant with no meta data.

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The Gaia Guardian's teleport block break (the bear trap cheese prevention) does not respect metadata (I did not test NBT, but can if you would like. I don't see how it would respect NBT and not the damage value/metadata).

You can reproduce by making (and using) a Gaia Guardian arena in a superflat with this preset: 2;7,44:7;0;

The only important portion of the string is finishing the block section with "44:(number greater than 0)".

When the guardian teleports on top of a slab, it will break the slabs on the ground and they will be Stone Slabs(44:0), not whichever slab you put on the ground.

FML Log: http://pastebin.com/23JpM7g4