I don't know if this is relevant to you now but I will answer for others.

I have this error again now and started digging for info. I have audio from YT playing, but if I send a clear mp3 file to the bot, it gives me this error.

1. 2880417800 - Specific ffmpeg error code. I don't know what it means. But it is a specific code, it does not change.
2. For Discord py it is best to use pytube and not YoutubeDL. YoutubeDL is a very slow and crooked lib. It is MUCH easier to work with pytube. If pytube doesn't work well, uninstall it and install it via pytubefix (pip install pytubefix).
3. I use the following ffmpeg_options: {'before_options': '-reconnect 1 -reconnect_streamed 1 -reconnect_delay_max 5', 'options': '-vn -filter:a "volume=0.15"'} If you remove “before_options” completely, mp3 files start playing normally. But there is a new problem - the bot sometimes stops playing music a few (10-15 seconds) after the start with the code ffmpeg 0 (although 0 means that the process is completed without errors). And how to fix it I don't know yet. *Without before_options will be: {'options': '-vn -filter:a "volume=0.15"'}