Well I was waiting for someone to say "But some eyepieces
should rattle" so I had better say it. It can be a sign that the glass is relaxed and being the shape it should. If you over-tighten all the locking rings and spacers inside the ep you can stress the lenses and then it wont work as good as before.
Some of the Meade wide field eps should rattle - I had a friend who took his apart to find our what might be wrong with it

only to put it back together and find the rattle still there.