If it helps, I can special case the 'G' lines, and always allow them through, changed or unchanged.

Most of the delay in metadata is for the Source ("Album", the 'Z' line) lookups. Those happen immediately upon recept of an 'F' line, and often result in waiting for the drive to spin up so that Hijack can read the tag file. This adds a 1+ second delay before the rest of the track data appears.

Were I to throw that into a background task, or not do the lookup until after the 'G' line, the available data would come out right away, and then later be followed by a new 'Z' line (and new 'D' line). But doing that is of limited value if the code remains fixated on having all data present when 'G' appears.

???