Incorrect parser response

[vadimlukutin]

I was have error on request for data structure.

[log] DEBUG 2022-12-04 00:59:46.539828:: GraphQL API Request QUERY AddCartItem
[log] DEBUG 2022-12-04 00:59:46.541269:: GraphQL API Request HEADERS {user-id: 914c20e2-1554-4458-869a-52761fd7f81f}
[log] DEBUG 2022-12-04 00:59:46.542483:: GraphQL API Request VARIABLES GAddCartItemVars {
cartId=07faeffb-833e-4cf9-be9b-cdc7e01578c5,
data=GCartItemData {
cartItemConfigurationDataList=[GCartItemConfigurationData {
comment=,
optionalModificatorIdList=[],
qty=1,
requiredModificatorList=[],
}],
productId=c5a59d1b-0341-4b75-9cee-00a57eee981b,
},
}
[log] ERROR 2022-12-04 00:59:46.566488:: LinkException(type '_$GCartItemData' is not a subtype of type 'GCartItemData' of 'object', #0 _$GCartItemDataSerializer.serialize (package:holla_client/core/data/remote/fragment/generated/cart_item.data.gql.g.dart)
#1 BuiltJsonSerializers._serialize (package:built_value/src/built_json_serializers.dart:103:18)
#2 BuiltJsonSerializers.serialize (package:built_value/src/built_json_serializers.dart:69:18)
#3 _$GAddCartItemVarsSerializer.serialize (package:holla_client/core/data/remote/mutation/generated/cart.var.gql.g.dart:33:19)
#4 BuiltJsonSerializers._serialize (package:built_value/src/built_json_serializers.dart:103:18)
#5 BuiltJsonSerializers.serialize (package:built_value/src/built_json_serializers.dart:69:18)
#6 BuiltJsonSerializers.serializeWith (package:built_value/src/built_json_serializers.dart:53:12)
#7 GAddCartItemVars.toJson (package:holla_client/core/data/remote/mutation/generated/cart.var.gql.dart:25:53)
#8 GAddCartItemReq.execRequest (package:holla_client/core/data/remote/mutation/generated/cart.req.gql.dart:42:25)

[knaeckeKami]

There seems to be an exception when serializing the request to JSON, so the issue occurs not in the response, but before even sending it.
To you have custom scalars/serializers?
Can you provide a reproducible example?