Hammer Coral Bubble; trying to be a bounce mushroom?

[JPM San Diego]

My hammer coral has developed a large clear bubble. It comes and goes. The coral otherwise seems to be in good health.
I have several pieces of this hammer coral around my aquarium. All of them are doing fine. Only one head has formed this structure.
Any idea what it is?

 

[reeferguy3303]

It’s just an indication that’s splitting. Nothing special

 

[Lost in the Sauce]

It’s just an indication that’s splitting. Nothing special

Can you give more information on this?

I've never seen this before on any splitting euphyllia. Only seen it on a torch that had fallen and damaged the flesh around the skeleton.