I won't be able to get too much info from Bosh because the keep all information solely for their people/service technicians but it does sound like the controls printed circuit is being affected by some type of PC failure.....
B22CS50SNS PartsAPPLIANCE 911
It's a normal noise! When the liquid refrigerant becomes less pressurised, usually when the thermostat clicks off,, it still bubbles through the system until the pressure equalises.
