I never got any problem wtih pairing my J3 to bluetooth device.
The problem I've had is - once I play the music on my Bluetooth headsets, the sound breaks very badly - loud buzzing, loud hissing, the singers sound like they have tuberculosis & on the verge of dying. I tried 3 different headsets (all of which, work fine on my sony player). So, I decided my J3 is a DOA, returned it, got a replacement, and still stuck with the same problem. Sigh.......
In the end, I purchased an external bluetooth transmitter (Blubridge) - happy ending, except the transmitter annoyingly takes space & swings about.