I have used this attachment before to seed black raspberries with no issues but today it broke the drive shaft.  This is a robust piece of metal!  Lucky it didn't break the Kitchen Aid Mixer!  I just used it as normal, putting soft berries in the hopper.  It jammed 3 times and made a concrete like blockage of seeds.  Almost impossible to clean and clear out. The 4th time it broke the drive shaft.  I seed the black raspberries to make jam.  It made jam all right -- JAMMED the machine!  It should be able to seed black raspberries.  No idea why it broke this time.  And you can't buy just this part.  The attachment doesn't work without the drive shaft.   I have to buy the entire thing if I want another one.  Not happy.