It is not reproducible and happens randomly. I will post the log when it occurs.
Meanwhile, from your experience, could it be anything else but a connection problem, that is when the server tries to send the INVITE to the callee using their saved IP and port but the operation fails? All my clients being behind NAT, I am suspecting an IP expiry issue. Wouldn’t it produce a 404 error in this case?
I am also wondering if a keep alive setting could help maintain the session alive…