Has anyone seen an emerald crab do this to a coral?

[BeejReef]

Not arguing with anyone... heck, there's a video of a bad emerald.
I've had good luck with mine so far. ofc, your mileage may vary.

I just think the OP has detailed a couple of recent changes to his system, so I'd not automatically jump to faulting the crabs.

 

[TheBeardedReefer]

When I added a second emarld crab to my system, he decided that he wanted to take up residence in my Stylo. Then he taught my other emerald crab to do it! Here's a picture of them both just hanging out in it. I did eventually get rid of the troublemaker because the Stylo got to where it didn't want to come out as much because he was always climbing in it. I do have a small dead spot like that as well where he would sit and block the light all day.

Also excuse the horrible lighting in the picture! It was before the lights came on and I was just trying to get the hilarious scene.

 

[Cell]

My emerald is great. He leaves my coral alone and actually sifts sand.