[teiafra]

With "video", I mean movie. Test the film titled "Borotalc1o" (by Carlo Verdone). Is it rendered properly?

Yes, absolutely. What I was trying to say, without sounding condescending, is that if the video starts playback, then everything is in the hands of Kodi, InputStream.Adaptive and the O/S. There are many combinations and variations, and I know for sure that the playback works fine on Raspberry Pi 4 and lower. So it might be a faulty driver/codec, or the old version of Kodi, that, I don't know. Some Raspbians and OSMC distros are known to have caused issues in the past, that's why I mentioned it. But, at the same time, since it's not a problem with the addon itself I cannot help you any further. If you want to do a stupid test, you might try replacing the Raspbian with a LibreElec distro, which is known to work much better in these conditions, but that's your choice. 

Thanks to all of you for the provided support 

just to add that I found somebody else reporting the exact same problem here https://forum.kodi.tv/showthread.php?tid...pid2939846
, not due to AmazonVod addon as such but surely linked to the video player and rendering