The buttons have filters that automatically adapt: if you let your finger on the button too long, it won't be detected anymore. Avoid touching the buttons for 10 seconds to let the filters reset.
If the left button, or the left and center buttons do not seem to work correctly, and your robot's serial number begins with the letter I, you could have a case of faulty waveguide. A faulty waveguide is obvious if you open the robot and observe it: there are holes at the place of the ejection pads. as it is not fully injected, it doesn't hold the buttons circuit correctly in place.
If you have a faulty waveguide, please contact us using the form at the bottom of this page and we will send you a replacement part.