Freepbx does not detect hangup of PSTN when going through IVR

I have a big problem…similar to the one described on this thread:

I am also using GXW4108, connected to Freepbx via SIP Trunk. I have an inbound route that points to IVR. When a PSTN caller dials the extension (after IVR prompt), and then hangup, Freepbx doesn’t detect the disconnect and continues to the user’s voicemail and in the process, leaving minutes of busy tone as voicemail message.

If I change the destination of the inbound route to an extension, the PSTN hangup is detected without a problem so I’m inclined to think that this is a Freepbx problem rather than Grandstream.

Please, if anybody has any idea how to fix this, let me know. This is the last problem I’m facing before we can switch to VOIP completely.

Never mind. Grandstream support solved the problem. For those having the same problem, make sure the Call Progress Tones all have the same frequency (most likely the autodetected busy tone).