These buttons or tactile switches can be cleaned if they are unresponsive, however replacing them will ensure they will work 100%.
Soldering is required.
This package will be sufficient for Traktor S2 controllers and any NI product with these same switches.
If you attempt cleaning the switches, first apply Isopropyl alcohol to the switch and work the button 40 – 50 times. Apply alcohol again and use compressed air to dry. Use a DVOM with the setting set to Ohms (resistance) and set the leads to opposite ends of the switches. While pressing the button, you should have continuity and no continuity when not pressing the button.
*Note: High level of soldering required to perform this task.