I made a test : if I put my watch on the right wrist : I have no disconnection, on the left, it is not stable.
Conclusion: the bluetooth signal is not as strong as the 5plus on the 5s plus. If you left hand like me, wear the Fenix on the right hand during your activity. It is a shame but this is the situation.
Several workouts on the left wrist with BT (notifications and music by phone) w/o problems. (fenix 5Xplus)
That depends on your headphones actually. If your headphone antenna is on the left side, then obviously you should use the watch on the left hand, if it's on the right? Obviously it should be the right, especially with Truly Wireless headphones.
I have the very same problem. It's a shame
Garmin fenix 5 plus, jabra elite sport, left hand - 7.60, 8.40 - dropouts :-( invested lot of money to watch and as well to earbuds to have premium experience.... so far I'm rather disappointed and desperately looking for solution.