Check the video to see what's going on.
Steps to reproduce the issue:
1. start meditation activity
2. press pause
3. Switch to mains screen with back button
4. return to activity with start button
After these, you can't resume activity or delete it. Later I figured out that swiping on display can lead me to the screen with Save / Discard buttons
I believe that it could be this bug I reported earlier, but I wasn't able to reproduce it reliably back then: forums.garmin.com/.../bug-frozen-watch-after-meditation