My focus is on surface-mount ceramic capacitors. The obvious failure extremes are open and short. Other than these extremes, can the failure be that the effective value of the capacitor is either higher or lower than the spec? Can this failure be intermittent in that it disappears when the technician eventually comes around to examining the circuit? I don't mean intermittent in the sense that it lasts seconds or less but that the failure lasts minutes but only at random time of day and random day of week.
If yes then I'm curious as to what the failure mechanism could be. Also, is there a test to confirm such a bad installed capacitor?