HRM-tri battery swap

On today's run a message popped up on my watch that the Heart Rate Monitor battery was low. It may well be linked to the cold weather but clearly it must be past its best. Luckily I keep a stock of CR2032 3V batteries in stock. There's a YouTube video of the process if, like me, you're not sure where the instructions are at home:

Note the the official instructions include a few extra tips.

Simply wet

The weather forecast was spot on, 95% chance of rain and it was. Anyway I was out of the house so committed to my usual 13km cruise to Oxstones. When I first bought the Garmin HRM-Tri I was interested in the R/L contact balance especially as I was always lop-sided. Then I forgot about it and noted that I was drifting closer to 50:50. Today's run is interesting in that I averaged 50:50 but started off to one side and moved across to the other.

If I'd been on a cambered road and gone 'there and back' it would be easy to explain. On a trail run where I was running around puddles it's hard to explain other than by linking to fatigue (or that the device simply drifts as it changes temperature and is thus useless?).