Hi,
possible reasons for ceramics capacitor failures:
* overvoltage - even spikes. Maybe at turn ON or turn OFF, or other situations. --> use overvoltage protection devices, or capacitors with higher voltage rating
* mechanical stress. Either vibrations or during soldering. Thermal stress --> keep on soldering recommendations and temperature chart
* chemical problems, like flux residuals --> try with usual cleaning. If problem persists use ultrasonic cleaning. (Take care that all other parts are allowed for ultrasonic cleaning)
Klaus