VPN rules disappear from firewall Pace 5268AC

Has anyone experienced VPN rule disappearing from the firewall on the Pace 5268AC? This issue happened both before and after the latest firmware. According to tech support, AT&T has no knowledge of this issue. The work-around is simply to re-add the VPN rule to the device firewall, but that’s not a great solution unless one is behind the firewall, which is why there’s a VPN rule in the first place. Maybe a timeout on the internet appliance somehow defaults the firewall rules (VPN is the only one in use)? AT&T tech support offered to change out the device with a different model but couldn’t guarantee that would resolve the trouble.