I am a service provider and we have deployed a HT818 ATA to provide multiple analog lines over a SIP connection. We have no issues getting the lines up, registered and calling in both directions. However, periodically, (up to several times a day) the PBX the FXS ports are connected to, stops getting dial tone and also receiving the ringing for incoming calls. A reboot temporarily fixes the issue but it repeats and the only correction is to reboot the Grandstream again.
We are running firmware 220.127.116.11.