The patient chair is what makes sit-down dentistry possible. The ability to have the patient reclined and low to the ground allows one to perform various procedures while seated. If there's a problem with the chair movement, your ability to treat patients is impaired at least and may not even be possible.
Most chairs have multiple points of control. They may have buttons or touch pads on the chair itself, a touch pad on the delivery system, or a foot control on the floor. There are many possible points of controlling chair movement. If there's a problem with chair function and you have more than one input (control), use a different control to see if function is restored. If so, you likely have a worn control.
Buttons and touch pads are frequently wiped down and disinfectants can get into the electronics causing them to fail. Smooth touch pads are better than older style buttons or switches at keeping the electronics safe from liquids, but they can still be damaged by disinfecting or just plain wear and tear.
Multiple controls will also have multiple connections to the main circuit board. Sometimes, the controls can be switched at the board allowing for more in-depth and expanded trouble- shooting. I've talked subscribers through the process many times saving them from the recommendation to "purchase a new chair". Before replacing a control, it's advisable to check the connections as well to make certain it isn't just a loose connection and to confirm the problem is in the control, and not where it connects to the board.