One of the rings should have a gap in it. It is part of the design. It is called a butt joint.
The design is rather old, actually over 100 years old now. That part is bent round so it
touches. This enables getting the disk in easily in the first place. However it does have
a couple of other uses, it gives the gyroscope a bit of give if it is dropped.
It also allows a little bit of adjustment, if too much pressure is on the shaft you can open the joint up a little.
If the gyroscopes shaft is not being contained by the rings it can be pushed together a little.
If there is bit of a gap you can push it together.