Ash.Error.Unknown.UnknownError: Invalid reference

11:29:38.679 request_id=GFIrFgeBN9WstPIAASCB remote_ip=127.0.0.1 [error] ** (MatchError) no match of right hand side value: {:error, %Ash.Error.Unknown{errors: [%Ash.Error.Unknown.UnknownError{error: "Invalid reference user.first_name at relationship_path [:user]", field: nil, value: nil, splode: Ash.Error, bread_crumbs: [], vars: [], path: [:filter], stacktrace: #Splode.Stacktrace<>, class: :unknown}]}}

11:29:38.679 request_id=GFIrFgeBN9WstPIAASCB remote_ip=127.0.0.1 [error] ** (MatchError) no match of right hand side value: {:error, %Ash.Error.Unknown{errors: [%Ash.Error.Unknown.UnknownError{error: "Invalid reference user.first_name at relationship_path [:user]", field: nil, value: nil, splode: Ash.Error, bread_crumbs: [], vars: [], path: [:filter], stacktrace: #Splode.Stacktrace<>, class: :unknown}]}}