class UsersStore extends Marty.Store {
  isCurrentUserAdmin(){
    return this.fetch({
      id: 'isCurrentUserAdmin' ,
      locally() {
        return this.state.isCurrentUserAdmin;
      },
      remotely() {
        return this.app.userQueries.isCurrentUserAdmin();
      }
    });
  }
}

is this example assume state.isCurrentUserAdmin assigned to true or false in the state UsersStore. When using it on the server side via Application.RenderToString the rendering hangs until max number of tries are reached and returns the string. The fetch remains pending throughout the iterations.

example diagnostic

  { status: 'PENDING',
    storeId: 'stores.UsersStore',
    fetchId: 'isCurrentUserAdmin',
    time: 121 }

  { status: 'PENDING',
    storeId: 'stores.UsersStore',
    fetchId: 'isCurrentUserAdmin',
    time: 1121 }

  { status: 'PENDING',
    storeId: 'stores.UsersStore',
    fetchId: 'isCurrentUserAdmin',
    time: 2121 }

it has to do with https://github.com/martyjs/marty-lib/blob/master/src/store/storeFetch.js#L153
where a statement trying to check existence of var result doesn't check for when result === false