Windows 11 doesn't show me the selected thumbnail for mkv videos

Hi, I've recently upgraded to windows 11 but I have a problem now: in windows 10 I created mkv videos with MKVToolnix and I could add a thumbnail adding an image and naming it "cover", as I did [here](https://imgur.com/a/ZvtY6qH).

But now on windows 11 it won't show me the selected thumbnail but it show me instead a random frame, usually the first or one of the first frames of the video ([https://imgur.com/a/ljVApSB](https://imgur.com/a/ljVApSB)); not only the new videos doesn't show the correct thumbnail, but also all the videos created previously in windows 10 now have lost their thumbnails.

Then I tried with another program, mp3tag, but as you can [here](https://imgur.com/a/tbvRwnk), it tells me that the video have already the right thumbnail (the one with the title "james II") so I can guess it's a windows 11 problem. Can you help me understand what is the problem?