Honestly, have watched the entire F1 season and lots of pre-season friendlies on Spark Sport so far - both live and on demand and not had a single issue.
Their Apple TV app came out early last week and Paul, I think their Samsung app came out early this week. So good chance you just got lucky.
The Apple TV app works very well. Would highly recommend if you don't want to arse around with TVs and Chromecasts also has Netflix, Youtube, things like Masterclass, Lightbox, tvnz, three, MUTV, etc