How do I make an enemy weak point? [SOLVED]

So in my game robots have a weak spot you have to shoot to destroy them, if you hit anywhere else the bullet will ping off of them.  I have the robots set to die after they play their death animation, so I have set them to play the death animation when a bullet hits their weak point. The photo attached shows the collision. The rectangle is the weak point and the circle is not.  I set the collision group to enemy weak point for the rectangle.
The other photo shows how I have this programmed.
I don't know why, but it doesn't work! If I change the required collision group to the robot it works fine!
Does anyone know another way to go about this?

What if you replace the "last collided actor" with the "of group" blue block (that one next to the "1rst actor" one)?

The "Kill bot" event is disabled.

Oh oops lol I fixed that.
It still doesn't work though, and I tried Creis' suggestion.

It seems to be a bug in the "Actor vs Member of Group" collision event.
However, the "Group vs Group" collision event works for your purpose.
See the attached image:

Oh it works! Thanks! That's the one thing I didn't try because I thought it would effect all of the bots on the screen but silly me, the last collided works there too. Thanks a bunch!