I am not sure if you are still looking for an answer, but if you do it might be worth checking the NestJS documentation on how you should idealy implement a mongoDB schema.

The documentation: https://docs.nestjs.com/techniques/mongodb

There they are describing a different more NestJS like way of defining the schema. It might help.

If it doesn't, please provide further information on how the AdminService and the MemberService is injecting the model/schema.