Why am I seeing inconsistent pressure readings on my espresso gauge?

If the gauge needle displays under-extracted zone (lower end) or over-extracted zone (upper end), check grind size and correct by adjusting accordingly - increase for upper and decrease for lower, also ensure appropriate tamper force is applied. Blockages may occur with incorrect filter basket usage; use Dual Wall baskets if using pre-ground coffee and Single Wall otherwise. Clean filter basket pins if necessary to resolve issues. (Page 15-21)