Diagnosis
The brew unit's compression mechanism is failing to compact the grounds, usually due to worn seals or coffee oil/gunk preventing full travel.
How to Fix It
Clean and inspect the brew unit.
1. Remove the brew unit (via the cleaning menu).
2. Check for obvious damage or worn brown rubber seals on the piston.
3. Clean it meticulously, paying attention to the rails it slides on.
4. While it's out, run a cleaning cycle (without the unit) to flush any debris from the chamber.
If That Didn't Work
The internal mechanism that drives the brew unit piston might be wearing out. This is a sign the brew unit may need professional replacement, common after several thousand cycles.
Heads Up
Wet pucks can drip and make a mess in the grounds container, leading to mold. Empty the container more frequently until you resolve this.