TWS does establish an SSL encrypted connection to port 443 at api.ibkr.com when fundamentals need to be requested. So you might want to check whether your network security software, firewall, or ISP blocks those connections intermittently. Would surprise me, though, since this is is no different than your browser going to https::/google.com.
You can check with your browser whether the connection works from your system. Just type in the address bar (not the search bar). You will see just a white page (and no error message) and you can verify the established connection by clicking the padlock in the address bar.
JR
