Playing your Roland CY-8 Cymbal time by time, it will becoming lack of sensitivity, you have to hit it very hard to trigger the sound. It is because oxidation is happening on the sensor inside the cymbal pad.
To fix it in very low cost without replacing a brand new pad, you may just buy a 27mm Piezo Elements Sensor from ebay, and then just replace the sensor disc inside the pad. Using a solder gun, detach the old disc and replace a new one. That’s it. The new disc will work like a charm.
For the soldering tools, I suggest you to use a ~45W solder gun, beware overheating will damage the disc. Never hold the heat on the disc longer than 5sec.