Just finished my run, and before saving, I thought I'd check my VOmax by swiping down on my Vivoactive 4. It discarded my activity.
It should not be this easy to discard an activity. I guess I hit discard and confirm in two inadvertent swipes. Swipe left/right to discard/cancel would prevent this accident.
Ideally, the watch should keep the last activity anyway, before it is saved (or there is a new activity).