I have a Forerunner 965 running 20.29 and have seen this issue twice in the past three weeks (both on the current software version and previous). When I set an alarm and delete it before it goes off, it's been going off the next day at the scheduled time even though I had deleted it. My watch does not show an alarm as being set, but it still goes off at the set time exactly one day later. This only happens once - two days after the original set time my watch is back to normal.