Rubber part from brewing unit

Hello everyone, I am in possession of the Melitta Caffeo Barista TSP and have just cleaned the brewing unit.
This I have disassembled and the following rubber part fell out. I have no idea where it went.



https://www.magentacloud.de/lnk/yxCmlRm4

The part sits at the very top of the brewing unit. Seals the riser pipe. Presumably it now pushes the coffee out the top of the brewing unit.

That's what it was. Thanks a lot.

2nd problem. When operating, the brewing unit makes a very loud clacking/cracking sound, as if something is not seated properly.

Ideas? Is there a part not installed correctly, maybe the silver metal clip inside the brewing unit?

You can operate the brewing unit times removed. Press the plastic tube in the brewing unit in which the spring sits, then it can be locked. Then you can operate them times by hand.

That worked too, top forum here.

Thanks a lot, the machine runs like the first day.