Default [Q] Galaxy Tab 3 call sound is awful

Device : Galaxy Tab 3 8.0 3G version (Model SM-T311)
CyanogenMod version : 11-20140309-UNOFFICIAL-lt013g
Android version : 4.4.2
Where I got the rom to flash from : http://forum.xda-developers.com/show....php?t=2557573

I just flashed this onto my device which was having a lot of problems with the stock rom (battery wouldn't charge, sometimes it would go from 70% to 5% in 5 mins, it was super slow/would hang etc etc).

Everything is working great except the call quality has the following problems :

1. If using speaker/handset : Strong echo + background noise for other party. I can hear distortions too but it is usable for me. The problem is for the other side.

2. Phone calls over bluetooth do not work. All I hear is some distortions, no actual sound comes through from the other side. Same for the other party.

This makes the rom basically unusable for me because I have to be able to make and receive phone calls. I really don't want to have to go back to the horrible stock rom so I thought I'd ask. Is there a fix for this? Can I perhaps use an older cyanogenrom that doesn't have this problem?

Any and all help greatly appreciated of course.