On a Bosch/Radionics control panel using popits, octopopits, or the card access interface modules. When there are two points addressed the same, the view point status shows "shorted" at the keypad or through diagnostics in RAM IV or RPS. When either one of the points are forced open, the view point status shows the point as open.
To verify this, take the point with a known location and remove it from the data loop. Be sure to continue the data loop to any other modules. Go to the view point status. If the point shows as anything other than "missing", there is another point with the same address.
There is no special troubleshooting method that will identify the duplicate point. Also pay attention to the different type of zone expansion available on the panel: Popits (D9127), Octopopits (D8128), and Card Access Interface Modules (D9210B).