DIAGNOSIS The vibration pump is failing or is obstructed. The pump cannot build sufficient pressure to push water through the system. This is often caused by scale clogging the pump inlet or a worn pump diaphragm.
FIX Perform an urgent descaling. Use a full-strength vinegar solution in the reservoir. Run multiple clean cycles, allowing the vinegar to sit in the system for 15-20 minutes between cycles. This can dissolve scale blocking the pump.
IF THAT DIDN'T WORK The pump itself is defective. The internal solenoid or diaphragm has worn out. The pump is a discrete component attached to the chassis with tubing. It can be replaced if you can source the exact part.
HEADS UP Running the pump dry or while obstructed will burn it out quickly. If you hear the noise, stop the cycle immediately. A failed pump often means replacing the entire unit, as the repair cost can be high.