
In the above image, pretend that the right side labels said "T line 2" and "R line 2, although don't know which would be on top. That would be similar to the way the OBi202 phone ports are wired.
In other words, the outer pair of the phone 1 contacts are in parallel with the phone 2 line. That is to permit use of a single 4-wire cable to connect to a 2-line phone.
You appear to have a short in your house wiring on line 2. Your action could be either
- replace the phone 1 cable with a 2-wire (single pair) cable
- isolate the outer pair on the connector that you plug the phone 1 cable into