Mesh bends, even tho it's only connected to ONE vertex group!

Hello!
Im making a robot in real life and designing it in blender.
Only to show how I want it to look and test mesurements.
So, I got this robot with an arm and 2 claws.

Now the problem is, I attached one claw, to one bone.
Yet, when I move that bone, the claw mesh gets deformed!!
It’s extremly enojing! How do I fix that?

Hello
check your Vertex Groups assignment ?!
Bye