[Asterisk-Users] Dumping outbound audio on hold

[Matt]

Hi,
I have a setup something like the following:

[callcenter] <--IAX2--> [voip-server] <---IAX2--> [LD provider]

I also have PRIs going in and out of [voip-server].

The problem is with calls going between [callcenter] and [voip-server].
When a call comes in the PRI to [voip-server] and then to
[callcenter], all is fine.
When a call goes out to [voip-server] and then to PRI, all is fine.
When a call goes out to [voip-server] and then to [LD provider], all
is fine, until I put the person on hold.   When I pick them back up,
sometimes outbound audio is dead (the person I called can not hear
me), however inbound audio is fine (I can hear them).

Does anyone have any thoughts on what this issue might be?