Weird problem. No Ringback with EC500 and cellphone OFF

[rsbowersett]

Strange problem here. Need help please!!!

Users on our solution are hearing no ringback tone when calling other users that have EC500 enabled, but their cell phones are either off or do not have service. The call is actually still processing, and will cover to voicemail eventually. However the caller does not hear ringback, and will hang up thinking the call is dead. This can be recreated on command. This issue only happens when the calls go through 2 SBC's on our solution.

Traces show nothing is off.
The same call with the cell phone ON, works.
The same call station to station, without going through 2 SBC's, works.
The same call from one of our area code (720) VPN phones, which is not on this solution at all, works. (No idea on this one...)


We attempted to resolve this issue by enabling the "Apply local ringback" setting in the configuration set on CM. This did resolve the ringback issue, but it introduced another issue.
If the same call is placed, and the cellphone is now ON, the called party picks up on the deskphone and receives one way audio. They can hear the other party, but cannot be heard.

Diagram of SBC's in our solution attached.

Help!