Please check to make sure that each bit adapter is free from damage or surface defect on the tapered mating surface each use before inserting them into the quick change. These defects include rust, nicks, burrs, excess dry thread cement, etc. Adapters that have surface defects will not fit properly into the quick change and can be dislodged from the machine during operation.
Especially check all new 1/4 shank bit adapters for excess thread cement on the set screws and tapered body surface. Excess thread cement on the set screws, or the body of the adapter, will prevent the adapter from fully snapping into the quick change. To remove thread cement from the adapter, use rubbing alcohol on a rag, or soft toothbrush, and wipe the excess thread cement off the adapter. Do not loosen set screws to clean the adapter.
Also, always make sure that each adapter and the inside of the quick change is coated with a light oil to prevent rust. For additional information on the general care of your machine please see the Care and Maintenance section in the Operators manual. As with your automobile, simple preventative care of your machine can prevent future required service.