I had this problem.
If it's like mine, the rabbit ears are loose on the pin. The rabbit ears and the circle emmiter area will swing left and right.
If you jam something between the rabbit ears and the little raised arms that the post attaches too it will act like a wedge, and provide stability.
To fix this I inserted a straightened staple in there, and then uses a knife to wrap it around the post. It's super thin, and BARELY even noticable.
But it provides enough tension to keep the emitter in position.
Hope that helps.