Hi Vincenzo,
I have seen a feel reels break in the past - the picture of the bailarm breaking on the Saltiga GT is not uncommon. Sometimes the old Z-6000 also break at the reel stem, because of the 3 holes that they drill through it to save weight which as a result also weakens it. They seem to have fixed this problem somewhat with the Dogfight.
I have had a reel (not a Stella) shear like the picture you posted above - this is rare though. For me, it was because the guy who assembled it after servicing did not put a part back properly on the shaft.
This is the first time I have seen a whole chunk of the oscillating shaft come completely off though!