https://www.zipp.com/..._Hubs_SM_ENGLISH.pdf
That is a link to the exploded view of the hub.
You can see that the only thing holding it all together is the drive side endcap.
This should be a firm fit.
There is no way the freehub can move side to side once on the bike unless the small spacer is missing behind the freehub body.
This spacer is quite thin and merely serves to prevent seal drag between hub bearings and freehub bearings so cannot explain the amount of movement you say occurs.
I would check that you have the quick release springs around the right way and that the axle fully seats in the frame.
The shifting problem you explain occurs with a non aligned hanger, and no a new hanger is is not necessarily aligned.
That is a link to the exploded view of the hub.
You can see that the only thing holding it all together is the drive side endcap.
This should be a firm fit.
There is no way the freehub can move side to side once on the bike unless the small spacer is missing behind the freehub body.
This spacer is quite thin and merely serves to prevent seal drag between hub bearings and freehub bearings so cannot explain the amount of movement you say occurs.
I would check that you have the quick release springs around the right way and that the axle fully seats in the frame.
The shifting problem you explain occurs with a non aligned hanger, and no a new hanger is is not necessarily aligned.