Inconsistent workout reminders on my Apple Watch Ultra 2

The workout reminder on my Apple Watch is inconsistent; for example walking, yesterday was spot on and today I walk 70 minutes and no reminder at all. (Ultra 2, 11.6.1)

at first I thought that the sleep time was the reason (setting from 2300 to 700 it doesn’t start before 700…). But I changed the sleep time and no change in reminder..

[Re-Titled by Moderator]

Original Title: Workout reminder