Offset between jukebox signal output and comparator output is random when disc is inserted with hopper

When a music disc is inserted into a jukebox, it becomes hard powered at a signal strength of 15, and a comparator can read the signal strength associated with the disc being played by the jukebox. The timing of these events should be consistent.

Steps to reproduce

Build a device that can compare the onset of two pulses deterministically. The attached video uses locking repeaters to do this. Attach a jukebox comparator output to one input of this device, and attach the jukebox directly to the other input. Feed music discs into the jukebox using a hopper.

Expected behaviour

The comparator output arrives one redstone tick after a music disc is inserted into the jukebox by all means, including via hoppers.

Observed behaviour

When inserting a music disc into a jukebox using a hopper, the delay between the jukebox becoming hard powered and the comparator emitting a signal is random. I have used a locked hopper to ensure that the music disc is always inserted into the jukebox with the correct tick parity (consume tick/produce tick).

Note

Droppers do not seem to exhibit this behaviour when the music disc is inserted.