Any chance that somebody from Voxalot team will react?
I don't think I'm the only person who have this problem Voxalot due to this situation with the quite common NAT keepalive method.
There is no need in receiving a reply in order to have NAT pinhole open, so it is still possible to receive incoming calls from Voxalot. But it is not possible to use the same trunk in Asterisk for placing calls to Voxalot, because Asterisk will mark Voxalot server unreachable.