How to re-tension the plastic saddle screw retaining discs
Grip the plastic disc carefully with long nose pliers, as shown below, and turn the adjusting screw a little clockwise, this should re-tension it.
If the gap between the saddle and bridge channel is too small to insert the pliers you may need to move it forwards. Once tightened you can move the saddle back to its previous position.
When setting the intonation please avoid the saddle coming into contact with the back of the bridge channel, as shown below, if this happens and you keep turning the screw it will loosen the retaining disc. If the disc does come loose you can retension as shown above.