I have a big problem with this router / modem. There is a sort of 60 second time limit beyond which I can no longer receive incoming calls. Outgoing calls always work. Unfortunately I don't see any reference in the VoIP configuration file as keep alive or something that can work in the same way.
Ok is not officially supported but being based on openwrt, it would be useful to understand if in the official versions, there is something similar to the keepalive on the telephone part. The router is rooted so if there is any string I can add it would be useful.