I've seen this in 14.08, 14.12 and 14.13, but only today have I been able to join together the puzzle pieces.
Occasionally the watch spontaneously thinks it's in an activity:
- Sensors connect if they're in range, and the notifications for that show in the upper part of the watch face.
- The Power Save timeout screen starts after 5 minutes.
If you view the watch face using a hotkey during an ongoing activity the watch, for the rest of that activity:
- Might drop GPS.
- Might disconnect sensors.
- Prompt for RD pod removal if that sensor had been connected.
- Re-enable touch.
- After the end of the activity it may be in enter an "in activity" state (eg. touch disabled).
This might also be the source of some people's "touch stopped working" problems.