NIVONA NICR646 - Spumatore no longer sucks milk

Hello together,

nearly 4 years ago I bought the CafeRomatica 646 from NIVONA. The machine delivers really very good coffee and I am actually so far fully convinced of the machine.

However, since a few days I have a huge problem and therefore I am very desperate:

When I want to prepare a cappuccino, the spumatore suddenly doesn't suck milk anymore. There is only hot steam coming from the nozzle

I have already tried the following to solve the problem:

1.) The spumatore was disassembled into its individual parts, placed in water for a while and then thoroughly cleaned again.

2.) after that it was checked again whether milk had settled somewhere, which prevented it from being sucked in.

3) the small air intake nozzle at the top of the spumatore was cleaned of milk residues with a small needle

4) the foaming nozzle was cleaned and checked whether milk residues had settled.

Despite these measures still no milk supply is possible!

What I still have to note:

1.) Hot water can still be obtained normally from the nozzle
2.) Steam is still produced.

However, I noticed something else that was decisive:

When I lift the container - in which the milk for frothing is located - a little high and the silicone hose is almost horizontal, suddenly something comes out of the frothing nozzle again.

Now I am completely helpless and hope you can help me with my problem.

Must also mention that I am an "absolute technical layman".

Thank you in advance for your help.

Andreas