Diagnosis
Rapid, under-extracted shots are a puck preparation or pressure issue. The top burr grind setting might be too coarse, or the machine's over-pressure valve (OPV) is stuck open.
How to Fix It
Adjust the internal top burr grinder setting to a finer setting (lower number). Ensure you are using the correct 54mm dual-wall filter basket for the dose, tamping firmly and evenly with the calibrated tamper.
If That Didn't Work
The machine's 15-bar pump might be delivering too much pressure due to a faulty OPV. This requires a technician to test and adjust the pump pressure down to the optimal 9 bars.
Heads Up
The Oracle Jet's grinder has two adjustments: the external dial for major changes and the internal top burr ring (under the hopper) for fine-tuning. You likely need to adjust the internal ring finer.