OXO Connect -Audio problems between 8038 and 8001G terminals

[Fabian-Setycom]

Hi everybody. I am writing from Argentina about a customer that has a problem with a brand new OXO Connect.
The system has around 80 8001G SIP terminals and 50 analog phones. The attendant terminal is an 8038 IP phone.
There is an audio problem when a call is established between a 8001G and the 8038. The 8001G can’t hear the audio coming from the 8038 in the first 5 or 6 seconds. After this time the audio is established, but the 8001 G user lost the first part of the conversation. On the other hand, the attendant on the 8038 side is able to hear the audio coming from the 8001G since the very beginning. In some occasions the 8001G user can hear some short audio coming from the 8038 at the beginning, may be for one second, after that the audio is out for 5 or 6 seconds, and then audio comes back again.
This anomaly happens randomly, it happens in all 8001G but not always. Sometimes the failure does not occur. We did some tests doing several calls from one 8001 extension to the 8038 and we found that after a call with the problem (mainly the first call we did), the following calls did not have any problem with audio. But if we waited some time after the last call, 10 minutes for instance, and we repeated the test again, the problem appeared again with the same behavior.
The audio problem also happens when the attendant receives a call from the public network (E1 PCM), the caller experiences the same audio behavior.
We changed the VoIP parameters several times (activating and deactivating direct RTP, echo cancelation, voice detection, etc) but no successful in solving the problem.
The Connect software release is R2.2.036, the 8001G firmware version 4.2.0.3-11364 and 8038 firmware version is 4.52.95
I would appreciate any help. Thanks.
Fabián