Custom IVR On Hook-Flash

So I have a Grandstream GXW-4008 Enterprise (Very similar to the HT502/702 but it has more lines)

I have it setup to send Asterisk a DTMF Event on Hook Flash.

When I press hook flash I don’t hear anything on the ATA but this comes up on the console:

[Jan 1 16:23:30] WARNING[699][C-00015e6d]: chan_sip.c:22538 handle_request_info: Unable to parse INFO message from 984123102-5068-3@BJC.BGI.B.BFB. Content

I would like the User (If they are in a call or whatever) To be able to press ‘Flash’ At any time to get to a custom IVR That says ‘Please Dial Extention (dial tone)’ And when they dial the number and press flash or tap the switch hook the call will be joined, Once they press Flash once more the person they added will be kicked out and so on so fouth.

It HAS To be my custom Context/IVR. It cannot be anything else.

The device appears to be sending an INFO message that chan_sip does not understand. Without implementing support for that it won’t get very far. If it were implemented, though, there is nothing really built to handle such a scenario in that way.