S0 owner since launch day and it’s never failed on me. The only issue is I have not updated the watch since WOS4.0. The reason being Apple removed Heart Rate Monitoring for the S0 in v4.1 and I doubt they will bring it back. At some point I will have to bite the bullet but it annoys the hell out of me:- Apple killed this usage and for that I am expected to buy a new model just to get it back!