Problem Tinker's Construct: cobalt shovel breaks instaintly?

[Acrobit]

So I've created a cobalt shovel with a magical stick and ardite binding. I've put 5 reinforcement plates on it with should make it unbreakable. But when I use my shovel in the area my builder worked in (wich is the explenation why everything is dirt in the video) it starts mining very fast and then breaks randomly.

Video evidence:

 

[Acrobit]

this is FTB revelation btw

 

[KingTriaxx]

Video Broken, but check the durability, I don't know how much magical wood multiplies it, and it might be a negative one. They will drop to 1 durability so...

 

[rouge_bare]

Magical Wood's Magically brittle has a chance of any tool with it instantly breaking, even if the tool would usually be unbreakable.