FR265 Firmware Version: 4.19 Stable
HRM Pro + Firmware Version: 8.8
Battery 90%
I have recently bought a HRM Pro Plus to use in Combination with my Forerunner 265 for the Lactate Threshold Guided Test and general use.
Unfortunately, I have found that the connection to the HRM Pro Plus is not consistent. When using the recommended ANT+ as Connection for the HRM Pro Plus and simultaneously listening to Music with my Bluetooth Ear pods (Samsung Galaxy Buds on 100% Battery), the Heart Rate starts to go blank regularly.
First artifact is about after ~15 Minutes of Running. The Heart rate displayed on the watch goes to "--" for 3 Seconds and then starts to pick up again, it then takes ~20 seconds for the heart rate to go to an accurate heart rate (where it was before the connection drop). This connection drop then increases in regularity the longer the run goes on, with connection drop intervals going towards every 2 minutes after 45 minutes of running.
This makes all the heart rate data garbage and a pain to work with (absolutely not what I expected when paying this money for Garmin Devices). I can confirm that as soon as I Pause the Music on the Watch - the heart rate drops stop, so there must be some interference or CPU load problem with that.
Picture of an example run where you can see the drops increasing in intensity and then stopping as soon as I pause music:
