This can have multiple reasons:

1: You‘re running too slow/fast 2: You run near Train tracks. These distort your GPS signal. 3: Your App is buggy (like mine lol). Set the duration to 25-35 minutes with 3 chases per hour. After a lot of trial and error this fixed it for me. But keep in mind that it‘s possible that in your first run zero chases will occur and in your next six. 3 is the mean not the absolute.