It's been mentioned before this is a *hardware* issue. Having the watch replaced will not help as the fault has not been resolved even on new watches.
Your best option is to return the watch and get a full refund.
If you need a *fitness tracker* with reliable functions, get a Fitbit Versa. I did and have never looked back. Sorry Samsung, but your Smart Watches are useless as fitness devices!
I have to re-register every time I come back to this site, despite using the correct log in details!!!
I posted the comment by gb10. Watch worked perfectly for 5 months when it stop tracking HR and switching on display with the gesture, while playing golf. Not the first time I played with it on. I sat quitely on the caddy and repeated the tapping procedure until the display switched on with the gesture, that was 2 weeks ago, and still going strong, again.
YES, it's a hardware issue. FIX it yourself and get on with your life!