This is really strange - but sometimes (and not everytime) when I hit lap split during a workout - my watch goes back to the clock screen like I'm not even in an activity.
The up/down buttons on the left just go through at a glance widgets and hitting the lap button again does nothing.
All indications are that you are no longer in a workout - BUT - if you hit start again to start a new activity - the watch goes right back into the activity like nothing was wrong.
What is going on? This has been happening for a few weeks now.