Unable to upload video files

Hello.

I'm having trouble uploading video files.

Has the following code:

    [ContentType(GUID = "1f7218e9-bddf-4734-b067-4d2d68b5dade")]
    [MediaDescriptor(ExtensionString = "mp4,webm,ogg,mov")]
    public class VideoMediaData : VideoData
    {
        [CultureSpecific]
        [Display(
            Name = "Name",
            Description = "Name of the video file",
            Order = 10)]
        public virtual string VideoName { get; set; }
    }

Have no problems uploading images and for example PDF files with similar solution.

Error messages I get when uploading video files are:
Object reference not set to an instance of an object.

Any thoughts on why it doesn't work and maybe some suggestion on some solution I can try?