MonarkI don't know how long warranty you have in your country. Please try your ASUS earphones with another phone. If they have low volume and distortion there too, then please contact your local ASUS support and ask if they are within warranty.
I am using asus headphones that came with the phone in the box i think the problem is in the headphones i am using it for 7 months constantly if it stops working where can i get this original asus Hi-res headphones please let me know@Anders_ASUS @LP_ASUS
I always had a doubt whether the headphones or the update causing this problem yesterday i tested with two other headphones they has no problem but let me know if there any chance to get this headphone again.