'Album Sort' - unexpected behaviour

[RSJ]

My understanding has been that if a tag 'Album Sort' is filled, then this is used rather than the contents of 'Album' to sort album names. However, I am getting some unexpected behaviour.

Previously, I have replaced 'Symphonies' and 'Nos.' with 'Symphony' and 'No.' in 'Album Sort' to ensure that albums are sorted in symphony order. This worked as expected.

However, recently, I decided to group symphonies by a particular conductor conductor together. So, in the 'Album Sort' tag I put 'Beethoven Symphony Haitink No. 1' and 'Beethoven Symphony Karajan No. 1', etc. While this sorted most of the albums in the order expected (i.e. the sorting was by composer-symphony-conductor-symphony no.), some were not. For instance, for both Karajan and Haitink, both their ninth symphonies were not in the Karajan or Haitink sequence.

Have I misunderstood the 'album sort' property?