I haven't used Cadimage for over 15 years, so I may be wrong, but if the tool is still API based this would explain the lack of compatibility between versions, though there should still be a seamless transition from one version to the next. However, Favorites are version dependent, though i'm pretty sure I can read AC23 Favorites in AC24, but not AC22 in AC23 or AC24.
Cadimage were acquired by Central Innovation who aren't GDL or API developers. So it would be worthwhile asking them what their development plans are considering you haven't seen any changes for a couple years.
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