Getting distorted images - possible error in decoder format?

[MarcinMroczkowski-Reakto]

Hello. I am using this decoder to decode video stream coming from Janus WebRTC. Now, it works, that means, it receives frames and decodes them, but the problem is, i am getting very distorted images.
This is incoming stream configuration in Janus:

rtp-sample101: {
        type = "rtp"
        id = 101
        description = "herelink"
        metadata = "You can use this metadata section to put any info you want!"
        audio = false
        video = true
        videoport = 5101
        videopt = 96
        videortpmap = "H264/90000"
        secret = "adminpwd"
}

Now, i set up the ffmpeg endpoint to decode this incoming stream:

VideoFormat videoFormat = new(96, "H264");
           _videoSink.RestrictFormats(format => format.Codec == VideoCodecsEnum.H264);
            _videoSink.SetVideoSinkFormat(videoFormat);`
           _videoSink.SetVideoSourceFormat(videoFormat);

Then, i save this frame to file:

Mat imageMatrix = new Mat((int)height, (int)width, DepthType.Cv8U, 3);
imageMatrix.SetTo(sample);`
Image<Rgb, byte> image = imageMatrix.ToImage<Rgb, byte>();
Console.WriteLine("creating photo...");
image.Save($"MIS_{missionId}_photo_{photoCount + 1}.jpg");

The above code is implemented using Emgu.CV, I get following image no matter if i use Rgb or Bgr format, it is always distorted:

Now, i do not really know where is the problem. Is it a problem with incorrect format? Does ffmpeg need to include h264 library? or is this the problem with actual decoding?

[MarcinMroczkowski-Reakto]

Follow-up explanation: Only the topmost part of the photo appears correct.

[MarcinMroczkowski-Reakto]

This photo is better, but still distorted: