Viber robotic voice issue on Noir A6 / Noir A8 / Noir A10 phones is now resolved. Someone has found an alternative Viber version, in which there’s no echo/robotic voice bug. You need to download and install Viber version 18.104.22.1682 from here (on your own risk) to enjoy a bug-free Viber experience on QMobile Noir series phones!
This problem was faced by almost all QMobile Noir series users. I even contacted Viber’s support to notify them about this issue, but their response was not very positive as they said it was not possible for them to test every phone and optimize it. It was understandable, as they can’t have access to Noir series phones as well.
Also tried to fix audio bugs by using audio library files from other MediaTek (MTK) phones to fix Viber robotic voice issue, but it was again of no use. Some library files even caused bootloop! So, had to revert back. Also, I don’t exactly know who discovered this particular version by testing. If someone knows the original guy, please let me know to credit him.
P.S. The latest version of Viber still has the robotic voice issue, so you can’t have a bug-free experience with the latest version.