If we connect a hopper towards and another out of a jukebox, they would be "activated" (i.e., locked) while the jukebox is playing, so no disc movement occurs.  When the jukebox finishes playing, it unpowers, allowing the hoppers to give the jukebox a new disc.  The whole process should take at most 2 ticks: the lower hopper takes away the disc, the upper hopper may need to wait for 0.1s, and then it should succeed in pushing a disc to the jukebox in the next tick.

But if the player leaves the area and unload the chunk when the disc is still playing, and leave the game, the jukebox no longer remembers that it is playing (this is marked to be "won't fix" in another bug).  The jukebox thus unpower.  But for some unknown reason (i.e., probably a bug), it unpowers for at least 0.4s, as can be seen in the experiment shown in the referenced video below.  This makes it unnecessarily hard to build a jukebox multi-disc loop, requiring a multi-component circuit rather than a simple 4-tick repeater.

Ref:

https://www.youtube.com/watch?v=OFQqkTPiXmA

Note: the quartz blocks in the video enclose exactly one chunk.