Thank you very much for your reply.
The problem was solved by
change sytanx from
score (1,2,3,4) (1,2,3,4) () () ()! items (1,2,3,4,5,6,7,8);
score (1,2,3,4) () (1,2,3,4) () ()! items (9,10,11,12,13);
score (1,2,3,4) () () (1,2,3,4) ()! items (14,15,16,17,18);
score (1,2,3,4) () () () (1,2,3,4)! items (19,20,21,22,23,24,25);
model item+step;
To
recode (1) (0)! items (1-25);
recode (2) (1)! items (1-25);
recode (3) (2)! items (1-25);
recode (4) (3)! items (1-25);
score (0,1,2,3) (0,1,2,3) () () ()! items (1,2,3,4,5,6,7,8);
score (0,1,2,3) () (0,1,2,3) () ()! items (9,10,11,12,13);
score (0,1,2,3) () () (0,1,2,3) ()! items (14,15,16,17,18);
score (0,1,2,3) () () () (0,1,2,3)! items (19,20,21,22,23,24,25);
model item+step;
As by default the category should start from 0...
Thanks.