Ran a 5K last Saturday equipped with single rS. Here is a screenshot of the recorded data:
which came from this run:
I attribute this result to a low battery condition 'fail soft'. Discovered the low battery condition after the race, put in a fresh one (no rechargeables for this bucko), but the data was the same. Ran another 4 miles with it the next day and it was its usual flawless self.
So the instruction is: ALWAYS check your battery level before critical data taking, even if it "should be" OK, or even if "it's been fine all week" or even if "it always lasts about a month". If you really want to be careful, just put in a new battery before any race.