After a couple of days research I came to know;
1.Bluetooth RF signals/rays travel through your body if your body acts as an obstacle(especially if the phone is in back pocket.)
2.Most of the humans are good conductors of RF waves.
3.But there are very few ppl on earth having less conductor abilities due to some unknown reason
4.Some times Cellphone or BT device chip is not strong enogh to send and rcv the signals in full capacity (weak chips)
To check whats the real issue ask couple of your friends to test your BT while connected with your cellphone (try to apply the same condition where you get isses e.g phone in back pocket etc.
Same goes with sync issue as for sync RF travel from one earbud to other through your face (if you are not a good conductor they can't )
If the things are happening same with couple of your friends then the either of your device has a issue in BT chip.
Plz don't forget to share the results.