Display order on Account Details form ARXCWMAI

This isn't consistent across instances.

One (test) instance returns Open transactions in descending Days Late within Class.

Another (test) instance mirrors Production in looking like ascending Days Late within Class and Source.

As far as I can tell all forms are on the same version, no folders, no sort.

Users want the descending Days Late display.

Any ideas why this would be different across instances ?

Am I missing something obvious ?