Reversed bitmap when creating AVI container

I have a list of images in my program, and I am generating an AVI video from them. For that purpose I use avifilewrapper_src library that handles the creation of video. The proces of creating is:

        Bitmap bitmap;
        //load the first image
        bitmap = (Bitmap)imageSequence[0];

        //create a new AVI file
        AviManager aviManager = new AviManager(paths.outputVideo, false);
        //add a new video stream and one frame to the new file
        VideoStream aviStream = aviManager.AddVideoStream(true, (double)nud_picturePerSec.Value, bitmap);

        if(chb_audio.Checked)
            aviManager.AddAudioStream(paths.sampleAudio, 0);


        int count = 0;
        for (int n = 0; n < imageSequence.Count; n++) {
            bitmap = (Bitmap)imageSequence[n];
            aviStream.AddFrame(bitmap);
            bitmap.Dispose();
            count++;
        }

        aviManager.Close();

If I keep giving different images, it works fine. If I however, put two similar images, than the video shows second image upside down (left/right side is correct). By two similar images i mean creating second image and copying it from the first one.

I have a feeling that this is somehow related to streams, but I can't find why are the images inverted.