Interval detection

We can’t see your activities like that. Next time post a screenshot please.

But probably, the Use Laps option is not enabled and then Intervals uses its own algo to hunt for possible efforts.
On the Activity Timeline tab, go to Actions at the bottom and choose Analyse with these options

If that results in what you want by default, change it on the settings page per sports category

There’s a thread explaining all the different ways of defining laps/selections/intervals here