Minecraft wiki entry for Jukebox, associated text: in Bedrock Edition, jukeboxes disable adjacent hoppers when a music disc is playing inside them, due to them emitting a redstone signal even without using a comparator. Because the hoppers are re-enabled when the song ends, a system of hoppers could be used to automatically eject and reinsert the disc when it is finished playing, causing it to loop. This does not work with a comparator though, as jukeboxes give off a redstone signal when there is a disk in the box. Since they do not eject a disk when a song ends, the jukebox keeps emitting a redstone signal when using a comparator meaning that the hoppers stay locked, preventing this feature from working.