The reference to the device's LINE port was a question to determine if your dropped calls were caused by an issue unique to having an external telephone line (POTS or some other VoIP service) plugged into the LINE port. Unlike all the other OBi products, the 110 has a line port, to enable users to make use of an existing analog telephone line as a way to place or receive calls, or to act as a calling bridge. It brings its own set of problems to the troubleshooting (related to issues with whatever telephone service is plugged into that port). Since you aren't using it, it's moot.
Like Mike said on June 30th, the problem could be caused by anything related to your ISP, your router's configuration, other stuff on your home network causing severe latency or dropouts, etc. I agree with Mike and Mango that the definitive troubleshooting procedure would be to analyze the network traffic.
Aside from that, some GV users do experience call disconnections. It used to be more of a problem, but Google has greatly reduced this issue. To determine whether you have a GV issue, or an OBi issue, you'd need to use your GV/Hangouts service without your OBi for a while, to see if the problem continues. Of course, if the trouble goes away, it'll point to the OBi.