Connect to Partner Not Working

I'm on Windows 10 using TeamViewer 12.0.75813. I'm trying to connect to a partner using Windows XP and the same TeamViewer version and it usually works, but AT LEAST ONCE A WEEK, I press the connect button, the "Ready to Connect" (with a green dot) turns to "Connecting" (with a yellow dot) and nothing happens. Now I can't connect again until the person on the other side restarts TeamViewer on his computer. ONCE AGAIN, THIS HAPPENS AT LEAST ONCE A WEEK, but the rest of the time it works fine. This is a huge inconvenience and needs to be fixed. If anyone has any ideas or solutions please help.