Custom resolver with @cypher schema directive do not accept Date as an Input

I`m trying to add custom resolvers to my grand stack app. There I get an error while passing DateInput to my mutation.

This is my schema:

type Registration @hasRole(roles: [admin]) {
  registrationId: ID!
  startDate: Date!
  endDate: Date
}
type Mutation {
CreateRegistration(startDate: Date!, endDate: Date): Registration
    @cypher(
      statement: """
      CREATE (registration: Registration {
                              registrationId: apoc.create.uuid(),
                              startDate: $startDate,
                              endDate: $endDate
                            })
      RETURN registration
      """
    )
}

This is my mutation, I use in the GraphQL playground:

mutation CreateRegistration {
  CreateRegistration(
    startDate: { year: 2020, month: 3, day: 22 }
    endDate: { year: 2020, month: 4, day: 12 }
  ) {
    registrationId
    startDate {
      formatted
    }
  }
}

this is the automated generated mutation by neo4j-graphql package:

20:49:51 api | 2020-11-29T19:49:51.949Z neo4j-graphql-js CALL apoc.cypher.doIt("CREATE (registration: Registration {registrationId: apoc.create.uuid(), startDate: $startDate, endDate: $endDate})
20:49:51 api | RETURN registration", {startDate:$startDate, endDate:$endDate, first:$first, offset:$offset}) YIELD value
20:49:51 api |     WITH apoc.map.values(value, [keys(value)[0]])[0] AS `registration`
20:49:51 api |     RETURN `registration` { .registrationId ,startDate: { formatted: toString(`registration`.startDate) }} AS `registration`
20:49:51 api | 2020-11-29T19:49:51.949Z neo4j-graphql-js {
20:49:51 api |   "startDate": {
20:49:51 api |     "year": 2020,
20:49:51 api |     "month": 3,
20:49:51 api |     "day": 22
20:49:51 api |   },
20:49:51 api |   "endDate": {
20:49:51 api |     "year": 2020,
20:49:51 api |     "month": 4,
20:49:51 api |     "day": 12
20:49:51 api |   },
20:49:51 api |   "first": -1,
20:49:51 api |   "offset": 0
20:49:51 api | }

this is the errorresponse I get back:

{
  "errors": [
    {
      "message": "Failed to invoke procedure `apoc.cypher.doIt`: Caused by: org.neo4j.exceptions.CypherTypeException: Property values can only be of primitive types or arrays thereof",

When I just use the autogenerated Resolver without @cypher, it works perfectly.

It looks like it is a problem with the input value for my date object. When I remove the date completely, it also works.

Does anybody have a suggestion, what I am doing wrong?

THX