On DJI Mavic
2S you active RTH by pressing and holding the H button on the controller, just like you power on your drone - you press once and press another time and hold it. This is how this drone works. I read it in the manual and this is what I always did in the past. If you do this, the controller starts double beeping just like in this case and it was double beeping for around 30 seconds and it switched to a single beep after that. So I did not cancel RTH, it was flying back home but something caused it not to return home. I waited over 40 minutes which is way more than the battery would have lasted even when hovering over the ocean, which means that it fell into the ocean.