| There should be a minimum thickness of friction plate and steel plate, in the manual somewhere, just check 'em with a vernier.
Also make sure you have the correct quantity of each plate.
Other things to check would be that the steel plates aren't warped, check them on a sheet of glass.
The other factor would be the springs, check for minimum length etc. I don't know if you can do it with Ducati's but is it possible to fit a washer under each spring to increase tension, it worked on my TLS | 
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