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I have noticed the same thing. At first I was annoyed at all the false activations, but then I realized it was just improved to actually respond.

Now that warmer weather has arrived and I’m not wearing long sleeves all the time, I’m looking forward to using this more.
 
After installing 5.2.1 my watch wouldn't report distance or activity. Just finished my morning walk and discovered I spent 15 minutes walking 0 ft with 0 active calories. Fortunately restarting the watch seems to have restored activity tracking.
 
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