Doesn’t seem like the server-side keepalive is helping; once that keep-alive times out, I suspect, and I’m not clear here, that the server needs to drop the connection – I’ve seen both Windows client and gl.inet client time out to the same gl.inet server in the same manner. Increasing the frequency of keepalive packets from the client-side did not seem to help.
Note: this is a NAT client - the keepalive from the server is likely to keep pinging the client forever; where that NAT client is quite likely to loose access to the ListenPort if it sits idle. One would think the keep alive would keep that UDP alive - but that does not seem to be the case, at least well enough to use gl.inet without logging into the admin page every now and then to bump the listenport.