When your adjusting on your amp. There isn't any resistance when turning the screw. Your only turning it back and forth to find the right bias.
When doing it on your watch. You have to turn the screw to make sure it's tight. At that point your just going to twist the end of the thin tip that fits into the slot off.
Also sure the one used for your amp has a thicker tip than the Panerai screw
Using a harder plastic won't help either. Will just snap right at the point needed to tighten that little more