aha...Anyway:
-The claws are not rough.
-Serving: (dont know).
-I thing the string has been twisted in the wrong direction. (i twisted it in the right direction) <--- just this could be a probblem?

*here are few pic's of claws and "twisted string direction" <--- (before: in the wrong direction).

Tnx! i hope, just this was the probblem.

Milan.