I have been using the Forerunner 245 for about 2 years and in the last 3 outings in conjunction with the Lap it does not record my heart rate while all other data are reported correctly. I use a Polar H10 sensor connected Ant +, the watch is synchronized at least once a week with Garmin express and has the latest firmware available. I did a master reset but didn't fix anything. The Polar H10 works perfectly and the battery is charged also does not give me problems with the 645 which I use in 90% of my outings. I downloaded and analyzed the .fit and actually every km for exactly 12 "does not register the HR it is as if it loses the connection with the sensor. I use both sound and vibration for the lap. Has anyone found the same problem? how did you solve it?
