I have still the exact same problem reported here https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-965/385923/alerts-getting-stuck-repeating-after-updating-to-20-29/1868496#1868496
I have the lastest update, including the one that is claimed to fix the problem but my alerts still get stuck often. I have to forcefully stop the connect app middle run to get it to stop playing alerts non-stop.