@mx4pro What version of Flyme are you and your mate on? I have a sneaking suspicion it may be a problem with Flyme 5.
There are many supposed fixes on Google but many don’t work with the rest being for Samsung devices and require editing build.prop files which I’m hesitant to try… Sucks. I’d settle for a way to increase volume using headphones but that doesn’t seem possible with Flyme :(
On my Meizu Pro 5 with Flyme 126.96.36.199i, doesn’t work and I am very sad. I do root, bosybox, SELinux Change Mode to “Permissive”, but nothing to do … I reboot many times for upgrade the driver and always the same thing = doesn’t work. I think that the problem is the version of Flyme which is based on android 5.1