When the music disk gets taken into the hopper minecart the song keeps playing & multiple songs can be played at once from one juke box, when the juke box is gone/broken the songs still keep playing, the songs will only stop playing after leaving & rejoining the world, which in this case is a single player world, for some reason it only happens with the render distance being 12 or more chunks, it is hard to recreate but I find that if it doesn't work after trying to put the disc into the jukebox 3 times then if you leave & rejoin/re-enter the world it will work, it may also take a few attempts, this bug is shown happening in the 1st & 2nd video, the 2nd video shows my f3 menu to show that I am on 1.20.1 (therefore also showing my pc's cpu & gpu, fyi I have 16gig ram but the allocated amount for minecraft is 2 gigabites, DDR4 aswell) & also shows that the music stops playing when you leave & rejoin the game.