some problems in a customer with 3CX

[com8]

We encounter some problems in a customer with 3CX On some calls, randomly, the call falls directly onto the voicemail. On the other hand, 8 times out of 10 , the call is answered and the phone rings.
In some cases, the phones automatically re-record, restarting the phone and displaying 3CX on the screen. The phenomenon is also random.
We made several tests (connection of phones with external power supply and not Poe, Dmz of the 3CX server, update of firmware of the Telephones Yeahlink T27P, etc.)

Do you have an idea or a configuration to advise us?

Thank you in advance.

 

[nub]

You need to make some extension to extension calls and find out if this can happen internally or only from a trunk simplifying the problem.

 

[leejor]

On some calls, randomly, the call falls directly onto the voicemail. On the other hand, 8 times out of 10 , the call is answered and the phone rings.

If you check the 3CX Activity Log, right after this happens, it should show that "attempt" to send an Invite to the set. I'm also assuming that, for some reason, the set was unreachable. Was it not registered, at the time? Check back further in the logs to see if it registers and un-registers on a regular basis. Perhaps there is a network (hardware) issue. You don't say if the sets are local, STUN or SBC connected, that can make a big difference, as more variables are involved