A few things that can cause your cursor to be erratic are:
1. Too high of sensitivity setting, which can cause signal falsing.
2. FAST Recovery set to ON will make the cursor more jumpy.
3. Very trashy ground will make the cursor bounce.....in this case you need to isolate your signal better by making short back and forth movements (aka Minelab wiggle technique) of your coil over your target. Try to wiggle only over the signal you intend to dig. That should stabilize your cursor a lot more.
4. Swing more slowly, and listen to each of the signals during your entire sweep of your coil. You need to move very slow with any Minelab coin machine to be successful.
HH,
CAPTN SE
Dan