In the first experiments, I was thrilled. After a few days I found the milk foam too cold and a little later came at a time the milk just ran out lukewarm, without foam is present - despite decent cleaning. In the subsequent drinks the foam was then sometimes ok, but sometimes again only lukewarm, unfoamed milk.
Using various search engines I have found the solution: the little piece of plastic which is in the tube and connects it with the steam nozzle attachment was to blame. No residues were evidently there to recognize. But if you use this adapter extra again "scrubs" in the cleaning, the foam then is always perfect.
The problem with only "lukewarm" foam I solve now so that I generate steam before cooking about 30 seconds before I "connect" the milk.