MWI tone still played when stutter=0 is set

[bradleyland]

Goal:
Keep MWI indicator lamp function, but have no MWI tone played.

Problem Description:
We have a set of T38G phones connected to a Kerio Operator (Asterisk) PBX. Everything is working really well, and we're thrilled with the phones, but I'm having a problem with the MWI tone playing on phones, despite having set configuration options that are supposed to silence this tone.

Some environment details:

PBX: Kerio Operator 2.2.3 build 2713
Phones: SIP-T38G
Firmware version: 38.70.0.186
Hardware version: 21.5.5.160.64.0.0

I attempted to follow the advice in an old Yealink UK forum thread "Voicemail Beep Sound". However, the phones are already configured with the parameters suggested:

Tab "Phone" > Menu item "Tones" > Select Country "Custom" > Field "Stutter" set to 0.

This option is set by the auto-provision scripts that are included with Kerio Operator (included below).

Attachments:

• reception-config-phone-tones.png - Screenshot of phone web GUI showing 'stutter=0' config.
• yealink_global.cfg - Github Gist of global auto-provision script.
• yealink_mac.cfg - Github Gist of individual phone auto-provision script.