1. Check for uneven casters with the chair both upright and upside-down.
2. Buy a matching set of new casters if you find any broken ones.
3. Pull each caster straight out to remove it.
4. Apply a small amount of spray lubricant to each chair base socket.
5. Tap each caster into its chair socket with a rubber mallet.
6. Flip the chair over and test out the new casters.
You can check the video below more easy for you to understand: