It may be getting ready to snap off the heavy head with intentions of drifting in the current in hopes of finding another location to reattach and form an new colony elsewhere?
Is this coral attached to the bottom or just burried in the substrate? It kind of looks like it has a bit of rot or fungus at/on/near the base that is causing this distress? Keep an eye on it and be ready to clip off any rotten flesh to prevent the entire thing from going south.
These are generally pretty resilient if you have to perform surgery, just do that early if it keeps getting worse.
Otherwise, I have no idea what is happening in this instance.