A few months back Miss Silvia suffered a broken part called the dispersion thread or water jet breaker. This stainless steel part goes between the dispersion screen and the big heavy brass disk. It cracked and since I had no replacement I soldered it up with silver solder. It held up for a week or so until I ordered a new one. Rancilio must have had complaints about this because the new part is machined very differently.
Old is on top, and new is on bottom. The difference is the post has much more material where it meets the larger flat area.
Here’s an image from a posting I made on Home-Barista a while back: