Strange behaviour when being put on hold / forwarded by remote end

Hi all,

I have a strange issue, when we do an outgoing call and are being put on hold, it happens almost every time that we hear our own music on hold and the call cannot be removed out of hold from the remote end. Even worse, the voice data is still being transmitted, so the far end can hear us, but not vice-versa.

I hope somebody will come up with an idea how to trace this.

Kind regards,