Yet another Chuck ?
Chuck,
1. Is the adaptor face contacting the shoulder of the spindle?
If the adaptor doesn't sit flush against the spindle shoulder, it is depending on the threads to center it. These won't do it. Perhaps the adaptor internal threads are not recessed enough and the thread bottoms on the end of spindle threads and won't go far enough to seat the adaptor against the spindle shoulder.
2. Is the adaptor seated completely in the chuck threads?
Here again, there may be a case of the threads interfering with the adaptor seating fully against the back of the chuck. These flat shoulders are what give the chuck its alignment.
Hope this helps.
Aloha, Tony