The symptom is when you play a mp4 video, you can only hear the sound but you cannot see the video. Also, if you are running in a terminal, you will see the error like "main decoder error: buffer deadlock prevented"
I tried to remove and reinstall it from the VLC official site, but I got the same result.
Here is the solution which works for me.
https://discussion.fedoraproject.org/t/how-to-fix-vlc-in-fedora-40/118009
sudo dnf install libavcodec-freeworld --allowerasing
rm -R ~/.config/vlc
