Forerunner 235 SW ver. 8.20. My calorie burn has dropped from a typical 260 calories to 44 o4 66 calories for the same 4.5 km fast walk. It's been around 260 calories for that distance for a long time. Nothing has changed, but the last two walks on May 16 and May 18 have been about 66 calories and 0 Recovery time. What has changed, and how do I fix it?