Hi, I have configured 1 grandstream gxw-4004 and 1 gxw-4008 with 3cx SBS. I have a one way audio problem when I use the attended transfer feature even in internal calls. Example: Extension 200 calls ext 201. ext 201 pick up the phone, press Flash key and call ext 202. Ext 201 hang up the phone. Ext 202 can't hear ext 200, but ext 200 can hear ext 202. I have the same situation from an external call. i attached the verbose log.