I noticed a bug that if an Alert happens while you're viewing UI3, the AI memo never gets populated for the newly added alerts on the list. It just stays blank. You have to refresh the UI3 page for the memos to show.
Increase timeframe for alert list background updates
Verify that the memo field gets updated retroactively
https://ipcamtalk.com/threads/blue-iris-ui3.23528/page-203#post-780503