[Q] d851 aux cable issue topic

Im sure some of you on here are aware of the d851's issue with aux cables specifically. what it appears to be is headphones will work, but when you plug into an aux cable in a car it acts like nothings plugged in and plays audio through speakers. at first i thought it was a rom issue as i only saw it with lollipop roms and was just gonna be patient for a fix, but now with stock rooted it still occasionally has the issue.
ive done about 30-45 minutes of googling and havent found anything pertaining to this issue. forgive me if i have overlooked something on here and please feel free to link me with anything ive missed on here or from another page. i just want to know more about the issue as far as what causes this to happen. is this hardware if i have it with stock rom now too?
thanks for your time :)

p.s. i see in another thread the att g3 has a similar issue. that thread didnt have a definite answer either though.