My forerunner 15 is displaying a slow hr, much slower than it used to. I have to really push myself to get it to what it used to display. I have tried updating using garmin express, buying a new strap, replacing the battery in the monitor, resetting the watch to factory default settings. I have also stripped the silicon from the old strap to see if it would read better, but no difference. Which leads me to belive it is an issue with the forerunner 15.
