I have a Forerunner 745 running version 7.60 firmware.  I typically use it with a Garmin HRM-PRO and a Stryd foot pod and a cheap Mpow Bluetooth headset.  I noticed the other day after completing an outdoor run while listening to my Amazon music playlist all was good and my run was tracked successfully.  After I completed my run, while still listening to my Amazon playlist, I decided to enable a Walking activity to track my distance while returning to my parking location.  During the walking activity, I turned OFF my Bluetooth headset, while walking and a few minutes later I noticed that my DISTANCE was no longer being tracked although the TIME was incrementing.  I tried to pause and resume the Walking activity but it refused to increment the distance.  The strange thing is that when my watch synchronized to Garmin Connect it showed me visually on the map the entirety of the distance I walked but the DISTANCE counter stopped at the moment I turned OFF my Bluetooth headset.  I have been able to recreate this bug several other times without fail in Walking and Hiking activities (didn't test it in Running activity) and its pretty consistent.  I must be listening to music (it's happened to me using the Amazon Music and the Podcasts application) during my Walking or Hiking Activity, and then at the very moment I turn OFF my Bluetooth headset, the DISTANCE counter will stop incrementing and trying to PAUSE/RESUME the activity will not do anything for the DISTANCE counter to increment despite the fact that it appears the watch is still logging my GPS information/path (since the path I travelled will stil appear in Garmin Connect).  I've tried restarting my watch and this bug still occurs whenever I am tracking an outdoor activity (Walking/Hiking) and am playing music (Amazon/Podcasts) and then turn off my Bluetooth Headset.  Keep in mind that everytime I tested I had my Garmin HRM-PRO and Styrd footpod paired to my Garmin Forerunner 745.