[PROBLEM] volume via rest api doesnt work with multiroom

[LeGuiz]

So I got a multiroom setup with 2 rpi, one is sender and one is receiver.

I connect a keyboard to the receiver rpi and use some trickery tricks to apply keyboard shortcut to 3 commands

one easy is "next" with 'mpc -h moode.local next'

then it gets tricky when I want to have volume up and volume down with each key press

I came to have something working with both command such :

curl -G "http://moode.local/command/index.php" -d "cmd=set_volume+up+5"
curl -G "http://moode.local/command/index.php" -d "cmd=set_volume+dn+5"

I can see the webUI changing volume accordingly when I press my keyboard but the 'real' volume doesnt change, until I click on webUI either + or - then it catches up with the volume accordingly.

(Oh and to complexify the setup, I also use the streaming url functionnality...if it interfere somehow)

Is this a normal behavior or a bug ? How can I get to control volume ?

Thanks