No RTP in the first 1-2 seconds after transfer

I have problem which I don't understand why is occuring.

I have an acme 3820. I have connected a provider SIP trunk, skype for business and a contact center (Sogedes).

When from Skype somebody calls the contact center, the caller hears immediately the announcement (welcome to XYZ company etc..,) but then when he is transferred to the cc agent, won't hear the first 1-2 seconds (for instance the greeting).

The interesting thing is, when somebody external, from the provide sip trunk calls to the cc, then the problem will not occur.

I had the idea to look for a solution around the latching, but it seems I don't 100% see how the latching, restricted latching should work or not the latching is the problem.