Location tracking

Dear community, on my iPhone11 I've switched off the possibility for most of my apps of tracking my location. Only a few are allowed 'when using the app'. Now it happens often that I'm not using the apps that I allowed to use my location, but still see this arrow appear indicating that an app is tracking my location. Even when I've closed all apps that are allowed to use my location. And when opening Privacy => Location services I don't see any app that used my location last hour. Who's tracking me?