We are seeing something very similar with asterisk shutting down websocket transports while the socket itself appears to stay open on the client side. It only appears to be an issue with the websocket transport, other transports are working as expected. The endpoints go unreachable until they re-register. I can confirm this behavior was introduced in 18.15.1 and that downgrading to 18.15.0 resolves the issue but I don’t like that as a solution as 18.15.1 is a security update.