I have some Smart Groups that have a trigger on the listing description text. Changing the listing description text does not automatically trigger the Smart Groups evaluation when the changed listing description text is saved.
Opening the Smart Group editor window and clicking the OK button DOES re-evaluate the Smart Group with the correct results.
The full text index gets updated on a background thread.
My theory:
When you change the description string, the smart group gets notified, and checks for matching items. But the change the full text index hasn’t been updated yet, so the immediate result might not be correct.