Problems with validation message

Description

Steps to reproduce

1) Add the following validator class:

public class Validator : IValidate<PageData>
{
    IEnumerable<ValidationError> IValidate<PageData>.Validate(PageData instance)
    {
       return new []{
            new ValidationError()
            {
               ErrorMessage = $"Error...",
               PropertyName = "Name",
               Severity = ValidationErrorSeverity.Error
            }
        };
    }
}

2) Open any page.
3) Make a change. (You should see a validation error by now.)
4) Click Schedule for Publish.
5) Choose any date and click 'Schedule'.

Expected: The validation error should still be displayed.

Actual: The validation error disappears