Recently removed cogs for the first time from early 2010 Campagnolo Chorus 11 speed cassette, and had a piece break off from the "special" 2.3mm spacer between 5-6. Then I noticed hairline cracks elsewhere. I'm curious if others have experienced this. The shop I purchased from will replace it. I wonder if there's a stress issue where the last loose cog meets the first cluster of 3?

I have 2000 miles on a broken one. I just pieced together and assembled back in place. I have a replacement ready to go the next time I pull the cassette. Glory cycles have them in stock.

My guess is that if it is misaligned and then compressed during the assembly, the spacer is damaged or cracked. I remember having trouble aligning the stack when the cassette was brand new. The next time I pulled it, the spacer was cracked.

Had one break; no idea why, maybe 9000 miles on cassette. Cheap enough to replace with many sources online.

Shop says Campy says it's from over torquing the lockring, and to only tighten to 15nm (of course 40nm is stamped on the lockring and in the instructions). I'm not sure I believe 15nm and I don't know who the source was for that. But yes, replacements seem readily available and not expensive, and mine is on the way, so I'm not sure why I even started this . Thanks for the replies.

If you torque the lockring to 15 Nm definitely use Loctite. I think 15 could be asking for trouble.

30nm has always worked for me.

But those spacers are plastic and sometimes crack. I keep a bunch around from worn out cassettes as replacements.

Replacement came in the mail today. Just want to say thanks to Wrench Science.