How to reset custom validation errors when using editform in blazor razor page

I have an editform using an editcontext:

<EditForm OnValidSubmit="HandleValidSubmit" EditContext="_editContext" Context="auth"><DataAnnotationsValidator /><input type="time" @bind-value="_foodTruck.EndDelivery" @onkeydown="@(q=>ResetValidation("EndDelivery"))"><ValidationMessage For="() => _foodTruck.EndDelivery" /><input type="time" @bind-value="_foodTruck.StartDelivery" @onkeydown="@(q=>ResetValidation("StartDelivery"))"><ValidationMessage For="() => _foodTruck.StartDelivery" /><input class="btn btn-default" type="submit" value="save" /></EditForm>

I do some custom validations in HandleValidSubmit:

EditContext _editContext = new EditContext(_foodTruck);private async void HandleValidSubmit(){  var messageStore = new ValidationMessageStore(_editContext);  if (_foodTruck.StartDelivery >= _foodTruck.EndDelivery)  {    messageStore.Add(_editContext.Field("EndDelivery"), "Bad time entered");    _editContext.NotifyValidationStateChanged();  } if (!_editContext.Validate()) return;}

What now happens is that my custom error ("bad time entered") is displayed at the right position. The only issue is: That error does not disappear when I change the value. So HandleValidSubmit is never called again if I click onto the submit button.

I also tried emptying the validationerrors when modifying the fields:

   protected void ResetValidation(string field)    {        var messageStore = new ValidationMessageStore(_editContext);                messageStore.Clear(_editContext.Field(field));        messageStore.Clear();        _editContext.NotifyValidationStateChanged();    }

This is called by onkeydown. But that doesn't seem to have an effect, either. The Errormessage does not disappear and so HandleValidSubmit isn't called either.