Check the headphones thread. Different headphones perform differently in different environments (indoors vs outdoors) as well as the location of the watch relative to the headphones (left wrist vs right and walking vs running).
I am experiencing a similar problem. While in the run, the music jumps a few milliseconds a lot of time. Very annoying. Even though I use the watch on the left wrist, which is te same side of the headphone receptor.
The problem seems to be the watch because I've tried several headphones, resulting in the same problem. I've also tested not during a run, it worked perfectly even with a certain distance, only dropping when I went to another room.
So probably the watch is not handling well the GPS and music, which is the whole point to buy the 645M.
Im on version 6.50.0.0
Any help?
I'm having the same issue. the music buffers when I'm running but plays fine when I'm not running. the watch can't handle tracking the run and playing music at the same time. does anyone have a fix for this?