scheme - Racket struct error: given value instantiates a different structure type with the same name -

i'm pretty familiar racket, , many in scheme , lisp family, have no idea error, or causing it:

network-biases: contract violation;  given value instantiates different structure type same name   expected: network?   given: (network ...) <-- omitted because useless. 

heres function error (i have gist of rest):

(define (update-mini-batch net mini-batch eta)   (define nabla-b (map (lambda (b)              (apply grid (shape b))) (network-biases net)))   (define nabla-w (map (lambda (w)              (apply grid (shape w))) (network-weights net)))    (define-values (nabla-b-new nabla-w-new)     (foldl (lambda (lst bw)        (define x (first lst))        (define y (second lst))        (define-values (nabla-b nabla-w) bw)        (define-values (delta-nabla-b delta-nabla-w) (backprop net x y))         (define nabla-b-new (+/ nabla-b delta-nabla-b))        (define nabla-w-new (+/ nabla-w delta-nabla-w))        (values nabla-b-new nabla-w-new)) (values nabla-b nabla-w) mini-batch))    (struct-copy network net            [biases (map (lambda (b nb)                   (- b (* nb (/ eta (length mini-batch)))))                 (network-biases net) nabla-b-new)]            [weights (map (lambda (w nw)                    (- w (* nw (/ eta (length mini-batch)))))                  (network-weights net) nabla-w-new)])) 

i couldn't mcve threw error, don't have 1 give.

the distilled basics of i'm trying in above function this:

• calculate new values structure's properties, , create new structure new properties.

- thanks!!

structures in racket generative. means each time

(struct network (num-layers sizes biases weights) #:transparent) 

is run, new type of structure created. these named network.

the error message see due evaluating structure definition twice (and bit confusing since 2 types have same name).

i can't see anywhere in code lead (struct network ...) being run twice. using drracket or alternative environment doesn't reset namespace?

if open "nn.rkt" , run it, see error?