DIAGNOSIS The spray head (showerhead) holes are clogged with mineral deposits and old coffee oils. This disrupts water distribution.
FIX Unplug the brewer and let it cool. Remove the filter basket. Look up into the brew head. You'll see a black plastic spray head with small holes. Use a stiff-bristled brush (a clean toothbrush works) and a paste of baking soda and water. Scrub the holes vigorously. Wipe clean with a damp cloth. Run a water-only brew cycle to flush.
IF THAT DIDN'T WORK The spray head may be permanently scaled. It is removable. Grip it firmly and twist counterclockwise. Soak it in white vinegar for an hour, then scrub. Reinstall by twisting clockwise until snug.
HEADS UP Never use a pin or needle to clear the holes. You can damage the plastic and worsen the distribution. Clean this every two weeks for best performance.