We have the Saeco Incanto at work. There is a horrible tatste that keeps re-occuring. I do try to rinse the brewing unit. Instructions say to the filter with the key, I cannot seem to get it off. I have also removed & rinsed the coffee dispensing unit. But the arm that it is attached to does not come off. What do you think is causing this awful taste? Am I not cleaning it properly. Please advise