Hi,
FOP2 just launches chanspy with the "w" option for whisper. After that, what happens is all asterisk and its configuration. If whisper works but stops midcall, then it is either an asterisk bug or misconfiguration or both.
Unfortunately, chanspy has a track record of issues and problems. You are using a recent asterisk release (but not the latest one), I do not remember bug fixes related to chanspy itself, but perhaps you can upgrade asterisk and see if it makes a difference or not.
You can also read chanspy help from the asterisk cli, read all the options you have and perhaps modify whisper_options in fop2.cfg and add/modify the options/mode for the command.
