Pause mixmon hangs up call

Hi, Im trying to configure the pause monitor application in asterisk 1.8.10 & fpbx 2.9

Im following the instructions as outlined here-

The feature works when I press the key, however instead of pausing the recording it always hangs up the channel!

I have tried with both automon and automixmon settings in freepbx, but always get a hungup call when I invoke PauseMonitor

Can anyone help??