I've always had a problem with the G string on my S series, equipped with ZR I trem ( as opposed to II ) lacking in sustain. I've managed to isolate the problem now; the string saddle itself is vibrating violently and all the string's vibration energy is being dissipated. I know it's the saddle 'cause when you play a note, you can hear the saddle rattle a little bit and also actually feel the vibration. Is there anything that can be done to secure it? The intonation screw is firmly locked down.