Asterisk and DVG-7022s. Asterisk loses registration SIP-client

Installed Asterisk version 11 or 13 with FreePBX 12. And installed Gateway DVG-7022s.

One FXS port the gateway registered on the Asterisk on number 100. His two FXO ports registered on Asterisk on 8 and 9 numbers.

For some time Asteris loses the registration of some ports (ports are different). Gateway displays preservation registration.

In log displayed periodically, every 10 minutes, registration gateway ports. But Asterisk still loses the registration of these ports.

Registration is recovered after restarting the gateway.

The following configuration SIP on the gateway:
TTL (Registration interval) [10 - 7200 s]: 600
Session Expiration [0 = disable, 10 - 1800 s]: 1800

What can be the cause of the situation? And her decision.

Igor Stepanenko.