I downloaded a video from the new server https://video.benetou.fr/w/rugsEB2sSbqgixNm2QjumH (but forcing IP 91.98.148.229 via local /etc/hosts) and uploaded back behind on same new server, thus behind the same reverse proxy (nginx 1.19) and it works no problem https://fabien.benetou.fr/pub/home/TestNewServer.mp4 so maybe not MIME types issue.