I am using this system in Singapore. The service provider is Singtel.
1. I have linked three analogue lines to it.
2. Yes, the problem is intermittent.
3. Yes, I can receive incoming calls.
Dropped call also happen while on conversation for outgoing call.
The 'ring once then dropped' issue occurs more frequently when calling Singtel mobile line. Land lines and other service providers mobile lines have much better success rate at 1st try.
The system is upgraded to SP2, and with latest firmware on the base station, gateway and phones. I have set the packet length to '40ms' on the gateway and phones which seems to improve the success rate. But it still happen, especially to Singtel Mobile line.